This section describes most of the BIOS settings that you will find in a typical Pentium-class or higher PC. Some BIOS settings are quite universal, while others can be found on only the systems made with one type of BIOS or made by one manufacturer. This section lists the most common settings that are used in modern PCs, with full explanations as to what they are and how to set them. This includes the more common advanced settings, but does not attempt a "shotgun" coverage of every setting I've ever seen on a machine. Some are very atypical and usually not something you need to worry about. The less common a setting is, the more often it is the case that you really will want to leave it on its default setting anyway. Not always, but usually.
By the nature of how I designed this section, it should cover 95%+ of the settings in your BIOS that you will ever want to change. If you find a setting in your BIOS that isn't covered here, you may find it in the BIOS Survival Guide, which has a more complete list of the settings found on various types of PCs.
For each setting I describe the most common options and what they mean. In addition, I indicate which options are usually the default. I also describe what the implications are of using the different settings, and provide general recommendations on how to configure most of the parameters. The settings themselves are organized based on the names of the settings groups you will find in a typical BIOS setup program.
Tip: It is a good idea to "back up" (record on paper) all of your BIOS settings once your PC is running and stable, and especially before you make any changes to them.
Tip: Reference this procedure for specific instructions on configuring the most important BIOS settings to safe values, to maximize the chances of booting a new or problematic system.
Note: Every setup program is slightly different from every other one. Even if
two BIOSes are both on Pentium motherboards and are made by Award, they may have different
settings. The commands as shown here might be different on your PC, or they might be in a
different place. Use care when modifying these parameters, and refer to your motherboard
manual if it is accurate.
Warning: The highly prudent will have a backup of their hard disk before
fiddling with their BIOS settings.
Warning: Changing advanced parameters can lead to system instability and data
loss. It is recommended that only users who really understand what they are doing change
these settings. Proceed at your own risk.
Warning: If your BIOS contains a "hard disk utility" that includes items like setting interleave ratios, low level formatting, or "media analysis", do not use it on an IDE/ATA or SCSI drive (which includes virtually every PC hard drive made in at least the last 5 years). These old utilities are designed for the MFM and RLL drives from the 1980s and can in theory damage a modern drive, for which they are unnecessary. I wish they'd just take them out of the setup program entirely (and on many newer PCs they have).
Standard Settings
Advanced Features
Advanced Chipset Features
PCI / PnP Configuration
Power Management
Integrated Peripherals
IDE Device Setup / Autodetection
Security / Password Settings
Hardware Device Settings / ("CPU Soft Menu")
Auto Configuration and Defaults
Exit Setup
This settings group contains basic parameters that you will normally need to set (or adjust) for your system to work properly. Most of these are present on virtually every PC.
Date
The system date. Make sure that you enter it in the correct format; normally this is mm/dd/yy in North America, but may vary elsewhere.
Newer versions of Windows will let you change the date within the built-in "Date/Time Properties" feature, and the BIOS date will be updated automatically by the system.
Time
The system time. Most systems require this to be entered using a 24-hour clock (1:00 pm = 13:00, etc.)
Newer versions of Windows will let you change the time within the built-in "Date/Time Properties" feature, and the BIOS time will be updated automatically by the system.
Daylight Savings
If your BIOS has this setting, enabling it will forward the time by one hour on the first Sunday in April, and drop it back by one hour on the last Sunday in October. The default value is usually "Enabled".
This setting is not present on most PCs; however, some operating systems, such as Windows 95, will do this for you automatically if you enable the daylight savings time option in their control settings.
Note: The date when daylight savings time "kicks in" can change in some cases; for example, a few years ago the spring date changed from the last Sunday in April to the first. If this happens again your BIOS will change the time on the wrong date so you will want to disable this unless a flash BIOS upgrade is made available to you that compensates.
IDE Primary Master
This is where the hard disk parameters are entered for the primary master IDE/ATA device, the first drive in a modern IDE system. See the hard disk section for details on what these terms mean and how these devices are set up. The various settings for the drive are discussed in detail in the IDE Setup / Autodetection section. The default setting for this on a system with IDE autodetection, is usually "Auto".
Note: Some older systems only have places for two drives' parameters to be
entered; often in this case they just call them "Drive C" and "Drive
D".
IDE Primary Slave
This is where the hard disk parameters are entered for the primary slave IDE device, the second drive in a modern IDE system. See the hard disk section for details on what these terms mean and how these devices are set up. The various settings for the drive are discussed in detail in the IDE Setup / Autodetection section. The default setting for this on a system with IDE autodetection, is usually "Auto".
IDE Secondary Master
This is where the hard disk parameters are entered for the secondary master IDE device, normally the third drive in a modern IDE system (though it can be the second as well, if the primary slave device is not used). See the hard disk section for details on what these terms mean and how these devices are set up. The various settings for the drive are discussed in detail in the IDE Setup / Autodetection section. The default setting for this on a system with IDE autodetection, is usually "Auto".
IDE Secondary Slave
This is where the hard disk parameters are entered for the secondary slave IDE device, the fourth drive in a modern IDE system. See the hard disk section for details on what these terms mean and how these devices are set up. The various settings for the drive are discussed in detail in the IDE Setup / Autodetection section. The default setting for this on a system with IDE autodetection, is usually "Auto".
Floppy Drive A
The type of the first floppy drive. The choices normally are:
This setting usually defaults to a 1.44 MB 3.5" drive, the most common type currently in use.
Floppy Drive B
The type of the second floppy drive. See common choices under "Floppy Drive A" above.
The type of the second floppy drive. The choices normally are:
This setting usually defaults to "none" or "not installed" since most PCs don't have a second floppy drive.
Video Display Type
This is the standard type of the display you are using; almost always this should be set to either "VGA" or "VGA/EGA" for a modern PC, if you are using any sort of VGA or SVGA card (which is basically every PC made in the nineties.) This is also usually the default value.
Halt On
Some PCs give you the ability to tell the BIOS specifically which types of errors will halt the computer during the power-on self test section of the boot process. Using this, you can tell the PC to ignore certain types of errors; common settings for this parameter are:
Warning: Telling the system not to halt for any error types is generally not wise. You
may end up missing a problem with your system that you will want to know about.
Virus Protection / Virus Warning
This setting has one of the most misleading names of all of the parameters in the BIOS. The system BIOS really has no way at all to tell which programs are viruses, and which are "wanted" programs. If enabled, what this setting does is to trap any and all writes to the hard disk's master boot record, and display a message to the screen each time asking if you are willing to allow the write. Since one common type of virus is the boot sector infector, this can indeed prevent the spread of these viruses.
However, this setting will also cause the BIOS to display its warning message for any legitimate access to the boot sector. So if you use any utilities that modify partitions, or even if you reformat your hard disk, this message will pop up rather unexpectedly. You can of course just "authorize" the BIOS, telling it to proceed with the write, but this can grow rather annoying if it happens often. It can also be quite confusing to someone who doesn't understand what this strange BIOS message means.
Some people prefer the safety of having this enabled, others find it annoying and turn it off. In fact, most people don't regularly run utilities that modify the boot sector. If you turn this setting off, you can probably find a similar feature, more elegantly implemented, in a memory-resident anti-virus program.
Internal Cache
This setting enables or disables the internal cache on your processor. This is also known as the L1 or level 1 cache. For 486 or later processors this should be enabled; turning off the level one cache will lead to a major performance hit. Earlier processors don't have internal cache, and enabling this setting can possibly lead to problems. You should disable this setting only for testing purposes if you are trying to find a problem, or if you suspect a bad processor chip.
On some BIOSes you may see three choices: "Disabled", "Write Through" and "Write Back". These refer to the cache's write policy. The write back cache policy will produce the best performance.
External Cache
This setting enables or disables the external cache on your processor, also known as the L2 or level 2 cache. Most 486 or later motherboards include this cache memory. Like the internal cache setting, this should be enabled at all times unless you are disabling it for troubleshooting purposes. Disabling the external cache will cause your system to slow down dramatically, but you can use it if you are having system crashes and suspect a problem with the cache chips.
On some BIOSes you may see three choices: "Disabled", "Write Through" and "Write Back". These refer to the cache's write policy. The write back cache policy will produce the best performance.
Note: There are some motherboards out on the market, particular PCI-based 486 motherboards, that have fake level 2 cache on the board. One way to test for this is to disable the external cache and see if there is a performance decrease in the system. If there isn't, you never had any level 2 cache to begin with. In addition, some systems will report (in the System Configuration Summary) the presence of enabled level 2 cache even when it is disabled. This is a BIOS that has been "doctored" and is a sign of fake cache on the motherboard as well. Amazing the trouble people will go to to cheat someone out of a few bucks, isn't it?
Quick Power On Self Test / Quick Boot
Enabling this setting will cause the BIOS power-on self test routine to skip some of its tests during bootup. One of the key things this setting usually does when enabled is cause the POST to skip checking all of extended memory for errors.
Most people enable this setting to speed up the boot process, but you should realize that you do increase the chance of the POST missing an error if you use this. Fortunately (or unfortunately) the POST memory test is virtually useless to detect transient memory errors (as opposed to hard errors that you would discover the first time you powered up the machine with the new memory in it), so once your system is running and stable, you can in most cases enable this setting safely. It's still safest to leave it disabled, which is what I recommend unless you have truly monstrous amounts of RAM. After all, how often do you boot the system during normal use?
Memory Test Tick Sound
When enabled, the POST memory test will make a tick sound as it counts up your system memory. Most people leave this enabled, others turn it off because they find the sound annoying. Many newer systems skip this option and turn the sound off entirely.
When building a system, it is recommended that you enable this, as the sound will act as a confirmation that your speaker is working, and that the POST is progressing normally. This is important during the first few boots of a system, and also if you are having video problems.
Boot Sequence
This setting controls the order that the BIOS uses to look for a boot device from which to load the operating system during the DOS boot process. Older machines do not have this setting; they look at the floppy drive first (A:) and then the hard drive (C:). Most systems will at least let you choose between "A:, C:" (the default) and "C:, A:". Newer systems will allow you to boot from the CD-ROM as well; in this case there will be six different combinations listed. The default will normally be "A:, C:, CD-ROM".
Note: Booting off the second floppy disk, B:, has not been an option on any PC I've
ever seen.
Some BIOSes are getting even more advanced in terms of the boot sequence options they will allow. Some systems will now allow you to boot off a different IDE hard disk than the primary master (C:), or let you boot from a SCSI device instead of IDE even when both are used in the same system (normally the IDE device gets preference).
Changing the boot sequence to seek from the hard disk drive first instead of the floppy disk drive has some advantages, and also some disadvantages. There are two main advantages. First, if the floppy disk isn't bootable, you virtually eliminate the chance of a boot sector virus spreading to your hard disk from a floppy. Second, you have a measure of security and reliability since when the floppy disk is bootable, anyone can write their own system files and boot the PC with their floppy, bypassing the standard startup files on the hard disk.
The disadvantages of not having the floppy bootable all relate to convenience. First, if you ever do have a virus on your PC then you will normally need to boot from a clean floppy disk to disinfect your hard disk; you will have to go back into the BIOS and change the boot sequence, disinfect, and then change it back. Second, there are some software programs that require their own boot disks (though they are becoming quite rare). Third, if your hard disk ever fails, you won't have any way to boot the PC. Some viruses manifest themselves by making the hard disk disappear. Finally, if you are installing a new operating system, or building a PC, you really need to be able to boot from the floppy disk.
S.M.A.R.T. for Hard Disks
Some BIOSes have a specific BIOS setting to enable monitoring of hard disks that support the SMART (Self-Monitoring And Reporting Technology) feature, which can allow the hard disk to report, under some circumstances, impending failures of the hard disk. . The normal default for this setting is "Disabled".
Power On Delay / Boot Delay
If you have the combination of a PC that boots up quickly, and a hard disk that takes a relatively long time to spin up, your BIOS may start trying to boot the operating system before the hard disk is read. A giveaway to this problem is the computer that won't boot when first powered on but will boot seconds later if the reset button is pressed. If your BIOS has this option, you can specify a time in seconds to delay the boot process. This is normally disabled, and should be unless you are experiencing this problem.
Boot Up Numlock Status
This setting, when enabled, automatically turns on your NumLock key when the system is booted. Most systems default this to enabled. This item is a matter of personal taste. There is also a DOS command (NUMLOCK) that can be put in the CONFIG.SYS file to enable the NumLock key. This will override the BIOS setting at startup if used.
Swap Floppy Drives
A useful feature for those machines that use two floppy drives, when enabled this swaps the A: and B: drives. This enables you to change the bootable floppy without having to open the case and switch the cable. Windows NT 4.0 does not properly support the floppy drive swap BIOS option; do not enable it if using NT. I have read reports of people getting stuck in the middle of NT installs because NT changed the floppy disk letters in the middle of the installation.
Floppy Drive Seek
Causes the BIOS to search for floppy disk drives at boot time. When enabled, the BIOS will activate the floppy disk drives during the boot process: the drive activity light will come on and the head will move back and forth once. First A: will be done and then B: if it exists. When disabled, this seek will not be done. Older PCs always did this seek; on newer machines it can be disabled to speed up the boot process. This setting will not affect the boot sequence, and vice-versa; if the boot sequence starts with A: the system will still try to boot from the floppy disk even if this is disabled, and if the boot sequence starts with C: the system will still look to C: even if floppy disk seek is enabled.
Boot Up System Speed
There aren't as many PCs that have this setting any more. Usually the options are "High" and "Low", where "High" is the normal system speed, and is the default setting. "Low" is for debugging only. Overall, this is a software equivalent of the good old "Turbo Switch" and on a modern system should be used the same way: that is, not at all.
Keyboard Installed
Some BIOSes let you specify explicitly if there is a keyboard in the system. The default is of course "Installed" (or "Yes", etc.) If you are using a PC without a keyboard (for example, for a file server or secured network PC) this will instruct the BIOS to skip the keyboard test during the POST.
Typematic Delay
This setting controls the automatic repeat capability of your keyboard. Usually specified in milliseconds, this controls how long a key must be held down before it begins automatically repeating. Typical settings are usually somewhere between 200 and 1000 milliseconds. Use what feels comfortable. Some higher-end keyboards have the equivalent function built-in. Setting this too low can cause the keyboard to repeat keys during normal typing, which can appear to be "keyboard bounce" and imply a hardware problem with the keyboard to the casual user.
Typematic Rate
This setting controls the repeat rate for the keyboard when the typematic feature is activated. It is usually expressed in characters per second. Use what feels comfortable, but don't go too high or you may feed the characters faster than the system can deal with them, which can cause beeping or even system lockups. Some higher-end keyboards have the ability to set this parameter built-in; sometimes it is called "Key Repeat" or "Repeat Rate".
Fast A20 / A20 Gate Option
In order to fully understand this setting you need to understand what the A20 line (21st address line) is and what its significance is. In a nutshell, the A20 line is used to control access to the high memory area, the first 64 KB or so of extended memory. This line is normally controlled by the keyboard controller. To improve performance, newer systems have this control function built into the chipset as well. To have the chipset control the A20 line and improve performance, enable this option. This setting is normally enabled by default. There is rarely any reason to disable this.
Video BIOS Shadow
This parameter, when enabled, turns on BIOS ROM shadowing for the block of memory normally used for standard VGA video ROM code, which is C0000 to C7FFF (32K). ROM shadowing in short, it speeds up your system by copying the contents of your video BIOS code from the slow ROM in which it resides into faster RAM. The default for this setting depends on the particular system a great deal.. Enabling it will increase performance. Disable it if it causes system problems, particularly those related to the video subsystem. On some systems the video BIOS shadow setting is named for the address range the video BIOS occupies, C0000-C7FFFh, instead of being specifically called "Video BIOS Shadow".
System BIOS Shadow
When enabled, this parameter turns on BIOS ROM shadowing for the block of memory that contains your system BIOS. This is normally F0000 to FFFFF (64K). This setting normally defaults to "Enabled". Since the system BIOS code is used so extensively, shadowing it can cause a great deal of system performance improvement.
C8000-CBFFF Shadow, CC000-CFFFF Shadow, etc.
Most BIOSes have several settings for shadowing each of the 16K blocks of RAM from C8000h through DFFFFh. These settings show up as something like "C8000-CBFFF Shadow", "CC000-CFFFF Shadow", etc., up to "DC000-DFFFF Shadow". Some systems have settings for ROM shadowing in 32K blocks instead of 16K, so you will see "C8000-CFFFF" instead of "C8000-CBFFF" and "CC000-CFFFF". (Some systems leave off the last digit in their notation, calling the blocks "C800-CBFF", etc. It's the same thing.)
When enabled, the setting selected turns on adapter ROM shadowing for that 16K block of memory. In short, it speeds up your system by copying the contents of any BIOS code found in adapters using this memory space, from the slow ROM in which it resides into faster RAM. The areas of memory from C8000 to DFFFFh are normally used by expansion cards such as network adapters. Turning on shadowing would speed these adapters up in the same way that shadowing the system BIOS speeds up the system BIOS code. However, things are much more tricky here, because some adapters use RAM as well as ROM, and map this RAM into this address space as well. If they do, and you enable shadowing, the adapter will malfunction because shadowing write-protects the RAM it uses (since it thinks it is emulating a ROM only, which cannot be rewritten). This can cause spurious results when using these cards, and can be very difficult to diagnose. In addition, normally unused areas of memory in this region are used as UMBs for loading drivers via the EMM386 driver, and enabling shadowing will cause this to malfunction. For this reason, the default for shadowing these adapter ROM areas is normally "Disabled" and I recommend that it be left that way in most cases. If you know all the details on the card whose ROM you are trying to shadow, enabling this can in theory increase performance, but it is not going to be anything very substantial in most cases. Incidentally, on most IDE/ATA systems, the block from C8000 to CBFFFh is reserved by the IDE hard disk BIOS.
This section of the BIOS setup program provides settings to "tweak" the chipset control parameters. Most of these settings are associated with fine-tuning control over the system cache, memory, and I/O buses, to optimize performance.
Warning: This section contains many settings that have the potential to screw up
your system. If after reading these descriptions you are not sure what a setting does, it
is usually best to leave it at its default setting. For most people, using some form of
the automatic configuration setting is highly recommended.
Cache Timing
This setting determines the speed that the chipset will use for reading data from the external (level 2) cache. This normally appears as something like x-y-y-y. In this case the parameter refers to the number of clock cycles to do a 32-byte burst read from the external cache line. Each entry in the cache of a modern PC is 256 bits wide; data is read from the cache using four consecutive 64-bit reads. The first read is normally slower than the others; this is the "x" above, and the next three reads are the "y"s. An example would be "3-1-1-1", which means it takes a total of six clock cycles to read from the cache. In general, the lower these numbers, the faster your system will be. How low you can drop them depends on your system, how fast your memory is, what clock speed your memory bus runs at, etc. If your BIOS supports an "Auto" setting for this parameter, using it is normally wisest, although it may not produce the highest performance results. You can try more aggressive settings (lower numbers) but be prepared to back off if you experience system problems, and don't go below the rating for your cache type.
Level 2 Cacheable DRAM Size / Cache Over 64 MB of DRAM
This setting controls how much of the system memory is "covered" by the level 2 cache. Using uncached memory on your system can cause it to slow down dramatically. You should always ensure that this value is set at least as high as the total amount of RAM in your system. However, for best performance, do not set it any higher than it needs to be.
Many motherboards using the 430FX, 430VX and 430TX chipsets will not have this option; it is most common on 430HX motherboards to select between 64 MB and 512 MB cacheability. You should in this case set it to 64 MB unless you are using more than 64 MB.
Note: This setting will not be present on Pentium Pro motherboards, since the Pentium
Pro uses an integrated level 2 cache.
Level 2 Cache Size
Some systems have a specific setting you must change to indicate how much level 2 cache you have on your board. Most newer boards do not have this setting and instead the hardware automatically detects how much level 2 cache you have. If you have this setting in your setup program, make sure it is correct.
Note: This setting will not be present on Pentium Pro or Pentium II motherboards, since these chips use integrated level 2 cache, not cache on the motherboard.
System BIOS Cacheable
On most systems, you can shadow your system BIOS ROM. Shadowing increases performance by copying the BIOS code from ROM to much faster system RAM. Enabling this setting will allow the system to cache this RAM as well, further increasing performance.
Normally you will want to enable this unless you are having a problem with your system and turning it off fixes it. If you have system BIOS shadowing disabled, this setting will be ignored.
Video BIOS Cacheable
On most systems, you can shadow your system BIOS ROM. Shadowing increases performance by copying the video BIOS code from video adapter's ROM to much faster system RAM. Enabling this setting will allow the system to cache this RAM as well, further increasing performance.
Normally you will want to enable this unless you are having a problem with your system and turning it off fixes it. If you have video BIOS shadowing disabled, this setting will be ignored.
DRAM Parity Checking
When enabled, turns on parity checking for the system RAM. This should be enabled if you are using parity checking (or ECC), and disabled otherwise. The default is normally "Disabled" since (unfortunately) most modern systems don't use parity memory. I recommend the use of parity memory;
Warning: If you turn on parity checking on a system that does not have parity memory in
it, the system will halt with a parity error as soon as it tries to boot up. If you turn off
parity checking on a system that does have parity memory, the system will run just fine,
but you will have no parity checking protection active.
DRAM Parity / ECC Mode
On a system that supports both parity and ECC error detection / correction modes--most newer systems support either both or neither--selects which mode is activated. ECC stands for "error correcting code" or "error correction code" and is a more advanced error detection and correction protocol than straight parity.
The default for this setting is normally "Parity"; it is ignored or disabled if "DRAM Parity Checking" is disabled.
DRAM Speed / DRAM Timing / DRAM Auto Configuration
There are a number of settings that control the timing of your system memory. Most setup programs now come with some sort of "automatic" setting that will determine what these parameters are for you. This is a "parent" setting of sorts that can be used to control the other individual timing settings on the screen. These parent settings normally come in one of two flavors:
When you use the "Auto" setting (either fully automatic or by selecting a memory speed) the BIOS will normally "lock" the individual settings that are controlled by this one, to reflect the fact that they are being set automatically by the BIOS. To unlock the individual settings so you can change them, you normally must turn off the "Auto" setting, or select "Manual". The default in most BIOSes is to enable automatic timing settings.
Warning: In a system that dynamically sets timing based on the detected speed of your memory, you must take care when using memory of different speeds. You should generally put the slower memory in the first bank, often called Bank 0. Otherwise, the system may set the timing too fast for the slower chips.
DRAM R/W Leadoff Timing
This parameter controls how many clock cycles are required for the first access to memory during a four-read "burst". In modern PCs, reads from the system memory are done in sets of four, because the level 2 cache used in the PC (which is filled by information from the main memory) is 256 bits wide (four sets of 64 bits). The timing, in clock cycles, to perform this quadruple read is normally stated as "x-y-y-y". The first read is slower because the address for the read must be supplied to the memory; the next three are faster because they are read consecutively from the first location (no need to supply an address).
Using the x-y-y-y notation, the Leadoff Timing setting refers to the "x" value, the number of clock cycles for the first read. On most BIOSes, this parameter is absolute, and refers to the actual number of clock cycles used for the first access. On others, this setting is the number of additional cycles required for the first access. For example, let's suppose the optimal burst timing for your system is 5-2-2-2. This means the first read takes 5 clock cycles, and the next three take 2 each. In most BIOSes, Leadoff Timing would here be set to 5. In some BIOSes, you would have a parameter called "Leadoff Wait States" or "Additional Leadoff Cycles", and you would put here 3 (the number of additional cycles required for the first read.)
The lower this setting, the faster your system will work. How low you can set this depends on your memory bus speed and the speed and type of memory you are using. In general, the faster your memory bus runs the more cycles it will take to access the memory unless the memory is also made faster. Putting this setting too low will cause memory errors; some of these can appear intermittently and be very difficult to diagnose. Using automatic timing to set this parameter is usually recommended.
By default most BIOSes enable automatic timing settings so this parameter would be "locked out" and not changeable; if you enable manual timing settings this setting will usually default to the slowest possible setting at first, for compatibility reasons.
Note: This setting controls the timing for both reads and writes. Some systems could have two different settings instead, one for read leadoff timing and the other for write leadoff timing.
Note: This setting is normally controlled by the DRAM Timing or Auto Configuration
mode, and if automatic settings are enabled you may not be able to change this.
DRAM Read Timing / DRAM Burst Read Timing / DRAM Read Wait States
This parameter controls how many clock cycles are required for the burst reads from memory during a four-read "burst". In most modern PCs, reads from the system memory are done in sets of four, because the level 2 cache used in the PC (which is filled by information from the main memory) is 256 bits wide (four sets of 64 bits). The timing, in clock cycles, to perform this quadruple read is normally stated as "x-y-y-y". The first read is slower because the address for the read must be supplied to the memory; the next three are faster because they are read consecutively from the addresses immediately following the first location (no need to supply an address).
Using the x-y-y-y notation, the Read Timing or Burst Read Timing setting refers to the "y-y-y" value, the number of clock cycles for the 2nd, 3rd and 4th reads of the four-read cycle. This setting will most often have options like "x-2-2-2", "x-3-3-3" and "x-4-4-4", although in some BIOSes the single number is used instead ("2", "3", "4".) Some BIOSes, especially on older machines, instead refer to read "wait states", which is essentially the same thing, except that it is one less than the number referred to above. A wait state is an extra cycle inserted for the processor to wait for the system memory. In the x-y-y-y notation, the "y" is the total number of cycles for each memory access. "x-1-1-1" is the best you can do, since it always takes at least one cycle. Zero wait states is the best you can do. So "x-3-3-3" is equivalent to 2 wait states.
Some chipsets will have a double value for this setting, with one used for EDO DRAM and another used for FPM DRAM. The system automatically detects which is being used; this is a sort of "semi-automatic" setting. In this case you may see options that look something like "x-2-2-2 / x-3-3-3" or "x-3-3-3 / x-4-4-4-4". The first timing number is used when EDO is detected and the second when FPM is detected.
Your system will operate fastest when this setting is as low as possible. How low you can set this depends on your memory bus speed and the speed and type of memory you are using. In general, the faster your memory bus runs the more cycles it will take to access the memory unless the memory is also made faster. Putting this setting too low will cause memory errors; some of these can appear intermittently and be very difficult to diagnose. Using automatic timing to set this parameter is usually recommended.
By default most BIOSes enable automatic timing settings so this parameter would be "locked out" and not changeable; if you enable manual timing settings this setting will usually default to the slowest possible setting at first, for compatibility reasons.
Note: This setting is normally controlled by the DRAM Timing or Auto Configuration mode, and if automatic settings are enabled you may not be able to change this.
Note: On some BIOSes this setting is combined with DRAM Write Timing / DRAM Write
Burst Timing. In this case the same timing is used for both reads and writes.
DRAM Write Timing / DRAM Burst Write Timing / DRAM Write Wait States
This parameter controls how many clock cycles are required for the burst writes to memory during a four-read "burst". In most modern PCs, writes to the system memory are done in sets of four, because the level 2 cache used in the PC (which is filled by information from the main memory) is 256 bits wide (four sets of 64 bits). The timing, in clock cycles, to perform this quadruple write is normally stated as "x-y-y-y". The first write is slower because the address for the write must be supplied to the memory; the next three are faster because they are written consecutively to the addresses immediately following the first location (no need to supply an address).
Using the x-y-y-y notation, the Write Timing or Burst Write Timing setting refers to the "y-y-y" value, the number of clock cycles for the 2nd, 3rd and 4th writes of the four-write cycle. This setting will most often have options like "x-2-2-2", "x-3-3-3" and "x-4-4-4", although in some BIOSes the single number is used instead ("2", "3", "4".) Some BIOSes, especially on older machines, instead refer to write "wait states", which is essentially the same thing, except that it is one less than the number referred to above. A wait state is an extra cycle inserted for the processor to wait for the system memory. In the x-y-y-y notation, the "y" is the total number of cycles. "x-1-1-1" is the best you can do, since it always takes at least one cycle. Zero wait states is the best you can do. So "x-3-3-3" is equivalent to 2 wait states.
Note: Systems that have a double value for read burst timing (one for EDO memory and one for FPM) will still have just a single value for write burst timing. This is because EDO is only faster than FPM memory when reading.
Your system will operate fastest when this setting is as low as possible. How low you can set this depends on your memory bus speed and the speed and type of memory you are using. In general, the faster your memory bus runs the more cycles it will take to access the memory unless the memory is also made faster. Putting this setting too low will cause memory errors; some of these can appear intermittently and be very difficult to diagnose. Using automatic timing to set this parameter is usually recommended. By default most BIOSes enable automatic timing settings so this parameter would be "locked out" and not changeable; if you enable manual timing settings this setting will usually default to the slowest possible setting at first, for compatibility reasons.
Note: This setting is normally controlled by the DRAM Timing or Auto Configuration mode, and if automatic settings are enabled you may not be able to change this.
Note: On some BIOSes this setting is combined with DRAM Read Timing / DRAM Read
Burst Timing. In this case the same timing is used for both reads and writes.
DRAM Speculative Leadoff
This is a performance enhancement available with some chipsets to speed up the (relatively slow) first access to system memory. In short, the memory controller "cheats" by starting the initial read request before the address for the read has been completely resolved. This can result in a performance increase. For best efficiency you will normally enable this. If doing so causes instability then you should disable it.
Note: This setting is normally controlled by the DRAM Timing or Auto
Configuration mode, and if automatic settings are enabled you may not be able to change
this.
Memory Hole
Some (unusual) expansion cards require access to particular memory addresses in order to function properly. This parameter lets you set aside the appropriate area of memory for these cards. The typical memory areas that can be set aside are "512-640KB" (the upper 128K of conventional memory) and "15-16MB".
This setting should be disabled unless you have a card that you know requires this setting. The default is normally "Disabled".
ISA (or AT Bus) Clock Speed / Divisor
This setting controls the speed of the ISA bus, in one of two ways. The less common way is for the setting to allow a direct setting of the ISA clock speed; this would include options of "6 MHz", "8 MHz", etc. The most common way is for the ISA clock speed to be set as a fraction of the PCI clock speed. The settings in this case will usually look something like "PCICLK/3", "PCICLK/4", "PCICLK/6", etc.
The setting to choose is the one that puts the ISA clock speed as close as possible to 8.33 MHz, which is the accepted standard maximum clock speed for the bus. Anything higher than this is considered overclocking. 8.33 MHz means that the correct option for a 33 MHz or 30 MHz PCI machine would be "PCICLK/4", while for a 25 MHz PCI machine it would be "PCICLK/3".
On some BIOSes there is an "Auto" setting as well that will pick the right fraction depending on the PCI bus speed it detects, but this is somewhat less common in my experience than other automatic settings elsewhere in the BIOS.
8-Bit I/O Recovery Time
This setting allows you to insert additional clock cycles after an 8-bit ISA I/O request. These are sometimes needed to slow down the processor after completing activity on the ISA bus, which runs much slower than the PCI bus. The default setting for this is usually 1 cycle. This can normally be increased to 5 or higher, or reduced to 0 (disabled). Normally you will want to keep this at its default setting.
16-Bit I/O Recovery Time
This setting allows you to insert additional clock cycles after a 16-bit ISA I/O request. These are sometimes needed to slow down the processor after completing activity on the ISA bus, which runs much slower than the PCI bus. The default setting for this is usually 1 cycle. This can normally be increased to 5 or higher, or reduced to 0 (disabled). Normally you will want to keep this at its default setting.
Peer Concurrency
This setting, when enabled, allows multiple PCI devices to be active at the same time. The default for this setting is "Enabled" and you will normally want to leave it on the default.
The settings in this section deal specifically with the PCI bus and Plug and Play (PnP) settings. PCs that do not have a PCI bus will of course not have this section at all; older buses such as the VLB did not have the features that this section of settings controls. The PCI bus for the most part takes care of itself, but the settings in this section can be used when particular behavior by the bus or expansion cards needs to be addressed.
Warning: This section contains many advanced settings that in the vast majority of cases you do not need to change. For most users, using some form of the provided automatic configuration setting is highly recommended.
Plug and Play Aware OS
This setting is shown on only some BIOSes. If present, enabling this tells the BIOS that you are using an operating system that supports the Plug and Play specification (such as Windows 95). When enabled, the BIOS will look for and initialize any Plug and Play cards in the system. Enable the setting if using Windows 95 or another Plug and Play compatible OS. The default is normally "Disabled".
Note: Some BIOSes will perform the initialization of Plug and Play cards
automatically regardless of the operating system being used, and will thus not have this
setting. Some will work fine with Plug and Play regardless of how this option is set.
However, on some systems that have this setting, Plug and Play may not function properly
if the setting is disabled.
PCI IDE Bus Master
Some BIOSes have an explicit setting to enable bus mastering of PCI IDE hard disk drives. If this setting is present in your BIOS and you are using PCI IDE bus mastering you should set this to "Enabled". Otherwise it should be left on the default, which is "Disabled".
Automatic Resource Allocation
There are several settings in the PCI / PnP Configuration section of the BIOS program that deal with assigning interrupt resources. This includes both regular IRQs and the internal PCI interrupt resources. For most applications there is no need to manually select or deal with these resources; in this case the default setting of "Auto" should be selected, to enable automatic resource allocation. Not all BIOSes have this setting.
When you use the "Auto" setting the BIOS will normally "lock" the "PCI IRQ and DMA Settings" (below) to reflect the fact that they are being set automatically by the BIOS. To unlock the individual settings so you can change them, you must turn off the "Auto" setting.
PCI IRQ and DMA Settings / IRQ <n> Assigned To / DMA <n> Assigned To
When automatic resource allocation is not used, the BIOS allows you to specifically designate which system interrupts (IRQs) and direct memory access channels (DMAs) you want it to be able to use for setting up Plug and Play devices. For each IRQ or DMA, except ones reserved by the system, you can designate either "PCI/PnP" or "ISA/Legacy". When a resource is assigned to "ISA/Legacy" it is declared "off limits" to the BIOS.
The IRQs that you can normally set here are IRQs 3, 4, 5, 7, 9, 10, 11, 12, 14 and 15. The DMA channels are 0, 1, 3, 5, 6 and 7. (The others are reserved by system devices.) The default on most systems for each of these settings is "PCI/PnP". If your system does not have automatic resource allocation (which is preferred) then it is usually best to leave these settings on "PCI/PnP" unless you are having a problem with Plug and Play. For example, if PnP keeps taking a resource for a PnP card that you need for an ISA card, you might want to set that resource to "ISA/Legacy" here to reserve it.
Note: If automatic resource allocation is enabled, these options will normally either be locked to prevent change, or even cleared from the screen altogether, since the BIOS will control them automatically.
1st / 2nd / 3rd / 4th Available PCI Interrupt
The PCI bus uses its own internal interrupts, usually numbered #1 to #4 or #A to #D. Some PCI cards need to be able to use one of the regular system IRQs (interrupt request lines) to communicate with the processor. This setting "maps" the PCI interrupts to regular system IRQs by telling the BIOS which regular interrupt line to use for PCI cards that need one. The usual choices for this are IRQ9, IRQ10, IRQ11 and IRQ12.
Note: If automatic resource allocation is enabled, these options will normally
either be locked to prevent change, or even cleared from the screen altogether, since the
BIOS will control them automatically.
PCI VGA Palette Snoop
The VGA "palette" is the set of colors that are in use by the video card when it is in 256-color mode. Since there are thousands of colors and only 256 can be used in that mode, a palette containing the current colors is used. Some special VGA cards, high-end hardware MPEG decoders etc. need to be able to look at the video card's VGA palette to determine what colors are currently in use. Enabling this feature turns on this palette "snoop".
This option is only very rarely needed. It should be left at "Disabled" unless a video device specifically requires the setting enabled upon installation.
This section contains the various settings that you can use to control your system's automatic power management settings. The pros and cons of using it are in this section on system care.
Note: In many ways, automatic power management is still "not ready for
prime time", at least in my experience. Enabling power management can cause problems
in your system because many software programs aren't prepared to properly deal with having
the processor power down or the hard disks turn off, etc. You can certainly use power
management, but be prepared to disable some of the settings if you have problems with
them. I strongly recommend disabling all power management features when initially
assembling a new system or performing upgrades or new software installations. If you do
not, you will have a hard time figuring out what is causing any problems you might
experience.
Global Power Management Setting
This is a setting that, if present, globally enables or disables power management. When set to "Disabled", the other settings in this section will typically be either locked out (so they cannot be changed) or else they will simply be ignored.
Video Power Down Mode
If present, this setting controls the method used to put the monitor into low-power mode. The typical options for this setting are:
Video Power Down Timeout
This setting controls how long the system must be idle for the video to be powered down. It is specified in minutes, or set to "Disabled". How long you set this for depends on your personal taste and how you use your system. Note that a colorful "screen saver" really doesn't save any power at all over regular use of the monitor--the monitor is still on and displaying information either way.
Hard Disk Power Down Timeout
This setting controls how long a hard disk must be left idle before it spins down. The default is "Disabled". In a system with more than one hard disk, an idle timer is normally maintained individually for each. The choice of setting here depends a lot on how you use your system, as well as your personal opinion on the question of whether or not hard disks are better off running continuously or spinning down when not in use.
Doze Mode Timeout
This setting defines the number of minutes before the system enters "doze mode", the first level of system inactivity shutdown. The exact definition depends on the system, but in general this mode means that the processor slows down to a minimal activity level while other parts of the system keep running as normal. The default for this setting is usually "Disabled".
Standby Mode Timeout
This setting defines the number of minutes before the system enters "standby
mode", the intermediate level of system inactivity shutdown. The exact definition
depends on the system, but in general this mode means that the processor slows down to an
even lower activity level than doze mode, and the video and hard disk drives are powered
down. The default option is "Disabled".
Suspend Mode Timeout
This setting defines the number of minutes before the system enters "suspend mode", the deepest level of system inactivity shutdown. The exact definition depends on the system, but in general this mode means that all system devices are shutdown (except for any that the BIOS is specifically told to keep running) and the processor is shut down to a trickle mode. The default option is "Disabled".
IRQ Wake-Up Events and Activity Monitors
When the system enters a power-down mode, it will look for activity to tell it when to wake back up. Normally you wake the system back up either by pressing a key or moving the mouse. However, you may want the system to wake up in response to other events. For example, you might want the system to wake up when activity on the modem is detected, if your PC answers incoming faxes. Some BIOSes give you the ability to specify whether or not activity on an IRQ will wake up the system.
The BIOS monitors the system for "activity" to determine when to enable power management. You can tell the system what it should consider activity and what it should not, in other words, what sorts of events on the PC should reset the idle counter for power management. For example, in almost every case a movement of the mouse or a keypress could be considered activity. However, if you have a sensitive mouse that can move slightly in response to vibration, you might want to set the BIOS so that movement on the mouse will not reset the power management countdown timers.
There will normally be a separate setting for each IRQ. For each one, the options will typically be:
The default for these depends on the system. Some BIOSes use similar controls with different names, or may separate the wake up event controls from the monitoring controls. If you are using power management you will want to tailor these based on what interrupts (devices) are in use on your system. Look here for information on what the typical IRQ allocations are on a PC.
Tip: For a system with a PS/2 style mouse, the mouse will be on IRQ 12. For a system with a serial mouse, the mouse will be on whatever IRQ is assigned to the COM port the modem is using. This is usually COM1, which uses IRQ 4.
Note: IRQ1, which is generated by the keyboard, is not usually listed here as it always causes a wake-up from power management, and cannot normally be disabled.
This section discusses settings that control your system's integrated peripherals. These settings are used to enable or disable integrated peripheral support, and set the various resources they use. If in addition to the standard integrated peripherals (serial and parallel ports, floppy and disk drives, etc.) you have integrated video, sound or other devices, you may find controls for them in this section.
Integrated Floppy Disk Controller
This setting enables or disables the integrated floppy disk controller (FDC). The default for this is "Enabled". If for some reason you are using a plug-in floppy disk controller card, you will want to disable the integrated controller.
Integrated IDE Controllers
This setting enables or disables the integrated primary and secondary IDE/ATA controllers. If you are using an add-in IDE controller card (which there is normally no need to do), or if you are not using IDE devices at all (for example, if you use SCSI devices), you can disable the built-in controller here.
On some BIOSes a single setting controls both the primary and secondary channels; the options in this case are "Disabled", "Primary", "Secondary" and "Both". Other BIOSes have two separate "Enabled"/"Disabled" settings, one for the primary channel and one for the secondary channel.
The default on most systems is to enable both IDE channels. This is usually an acceptable setting for most PCs, but some systems can exhibit strange behavior if the secondary IDE channel is enabled but there are no drives on it; for example, Windows 95 may try to set up a drive controller device on the secondary channel and then get confused when nothing is on it. It is therefore prudent to disable the secondary IDE channel unless you are using it. This will also free up the IRQ used by the secondary channel (IRQ15) for use with other devices, if you need it.
Integrated Serial Port 1 / Serial Port 2
This setting lets you specify the resources for the first and second serial ports on the motherboard. The exact name used for the various options varies (some call them "COM1", "COM2", etc. while others just list the I/O address and IRQ options). For each serial port setting you will typically find these:
Normally you will set the first serial port to the resource settings for COM1, and the second to COM2. If you are using an internal modem and you want it to be set up by your system as COM2, the easiest way to do this without generating any conflicts is to disable the second serial port here, to prevent interference.
Integrated Parallel Port
This setting lets you specify the resources for the integrated parallel port. On most systems you are allowed to choose one of the typical resource settings allocated to parallel ports, or to disable the port:
Integrated Parallel Port Mode
Parallel ports have several different modes of operation. The original parallel ports were used only for one-way communication from the PC to the printer; newer ones include bi-directional communication and other abilities. The normal choices for this setting are:
Generally speaking, you will usually want to use EPP or ECP. ECP has enhanced performance but greater compatibility problems, overall. I usually use EPP.
Integrated Parallel Port Mode
Parallel ports have several different modes of operation. The original parallel ports were used only for one-way communication from the PC to the printer; newer ones include bi-directional communication and other abilities. The normal choices for this setting are:
Generally speaking, you will usually want to use EPP or ECP. ECP has enhanced performance but greater compatibility problems, overall. I usually use EPP.
PS/2 Mouse Enable
On systems that support a PS/2 style mouse, this setting enables or disables this port. If you are using the port you should enable this, otherwise you should disable it so that the interrupt reserved for the PS/2 mouse (IRQ12) can be used for another purpose. Some systems have an "Auto" setting for this parameter, which is really ideal, since it will only enable PS/2 support if you actually have one connected.
USB Enable
Use this setting to enable USB (Universal Serial Bus) devices on motherboards that support USB. If you are not using USB, leave this setting at its default ("Disabled").
This section discusses the BIOS settings that control the setup of IDE/ATA devices (particularly hard disk drives). Most BIOSes have an entry in the Standard Setup menu for each of the four IDE/ATA devices supported in a modern system (primary master, primary slave, secondary master, and secondary slave). For each one, you can enter a value for each setting in this section (type, size, cylinders, etc.)
It should be noted that all modern hard disks use special technologies that makes simple geometry figures like "cylinders, heads, sectors" inapplicable. For example, almost all modern drives use a variable number of sectors, and are set up using an "approximate" figure in the system BIOS. This isn't something you generally need to worry about as you set up your hard disk, but remember that if it says "63 sectors" that doesn't necessarily mean the drive really has that number in each cylinder. In fact, it normally will not. This subject is covered in some detail in the section on hard disk geometry.
Virtually all BIOSes now come with IDE device autodetection. This comes in two forms:
When you use dynamic autodetection, the BIOS will normally "lock" the individual device settings that are being automatically set by the BIOS at boot time. Most systems that provide manual autodetection will not lock the individual settings; they autodetect, set the settings, and then let you change them if you want to. In most cases of course, you will not want to change what the BIOS detects.
Most BIOSes that allow dynamic autodetection also allow manual autodetection; the choice is yours. Using some sort of autodetection for IDE/ATA devices is strongly recommended. It is the best way to reduce the chances of disk errors due to incorrect BIOS settings. It also provides immediate feedback of problems; if you can't autodetect a drive from the BIOS, you know you have a problem even before you try to boot up.
Note: On most BIOSes, you perform a manual IDE autodetection using a special entry with that name on the BIOS setup program menu. This entry autodetects all IDE/ATA devices, one at a time. However, other BIOSes "hide" autodetection. For example, on some BIOSes you autodetect an IDE/ATA device by moving to the "Type" setting for the device and hitting {Enter}. This runs the autodetection for that device only. Check your manual if you are having problems finding the autodetection facility.
Warning: If your BIOS contains a "hard disk utility" or "low-level format" type program, do not use it on IDE/ATA drives. These utilities are intended for older MFM and RLL type devices. Modern IDE drives do not need low-level formatting, interleave factor settings, or media analysis under all but the very most unusual circumstances, and when they do need it, they need special utilities specially designed for the type of drive you are using.
Type
This setting determines the "type" of the IDE device. In the early years of the PC, there were few different types of hard disks, and there were far less sophisticated BIOS setup programs. There was no autodetection for hard disks, and no way to manually enter the parameters for the hard disk. You selected the "type" (really a number, usually from 1 to about 45 or so) of the hard drive from a predefined table that was hard-coded into the BIOS. Different machines would have different tables, and newer machines would have more newer drives in their tables than older machines did. If you tried to put a new drive in an older machine you might find it had no entry that matched, and you'd have to use the "best fit" entry you could find, sometimes losing some of your drive's capacity. Overall, it was a big pain.
Newer BIOSes don't restrict you to using the entries in the fixed "disk type" table, although the table of fixed entries still persists. In today's BIOSes, you will normally have the following options for each device's "Type":
Note: Instead of "User", some systems use the last number in the table for
user settings. If entries 1-46 for example are predefined drives, the BIOS may call the
"User" setting "Type 47". It's still the same thing, just with a
different name.
Some BIOSes implement manual autodetection of IDE devices using the "Type" setting. By pressing {Enter}, the BIOS will autodetect the device, set the type to "User", and set the other numbers and options for you. Most BIOSes however have a dedicated menu entry for autodetecting all IDE devices.
If you select anything for "Type" other than "User", the BIOS will lock the "Size", "Cylinders", "Heads", "Sectors", "Write Precompensation" and "Landing Zone" settings, since these will be determined either by reading the fixed table, or by dynamic autodetection (if you select "Auto"). CD-ROMs do not use these physical geometry parameters since their construction is totally different.
If your system supports the "Auto" setting, you are generally best off using it. This will ensure that your system is always set up correctly. You should set to "Disabled" any devices you are not using, and use "CD-ROM" for IDE CD-ROM drives.
Note: Some BIOSes do not have a "Type" entry for CD-ROMs, but will autodetect a CD-ROM at boot time. In this case, it is best to set that device to "Auto".
Size
This setting indicates the size of the drive, normally in decimal megabytes. This actually isn't really a "setting" per se, since you don't normally enter this value. It is calculated according to the following formula:
The 512 is because PCs use 512-byte sectors; the 1,000,000 converts the number to decimal megabytes. The number of heads, cylinders and sectors in this formula is equal to whatever the settings are in the BIOS.
Cylinders
The number of cylinders on each side of each platter in the disk. For older drives, this is the number of physical cylinders the disk uses. For newer disks, it is the logical number of cylinders that the drive specifies for use in the BIOS setup; see here for an explanation of physical and logical geometry.
For newer drives using BIOS geometry translation, the BIOS reduces the number of logical cylinders by dividing it by an integer factor (2, 4, etc.) so that it is less than 1,024 (the BIOS limit for the number of cylinders for historical reasons) and then multiplies the number of heads by the same number.
For example, a Western Digital Caviar 33100 3.1 GB drive has nominal parameters (logical geometry) of 6,136 cylinders, 16 heads and 63 sectors. When you set up this drive (autodetect it) most BIOSes will record 767 cylinders, 128 heads and 63 sectors. Of course the drive doesn't really have only 767 cylinders, but this is the way that the BIOS gets around the infamous 504 MB restriction. See here for more details on BIOS translation.
Note: Some BIOSes will continue to show the actual physical parameters even when set to a translating mode like LBA. This can be confusing to see on the screen, but if the BIOS is set to "LBA" or "Large", it should be using the translated parameters internally.
Note: IDE autodetection will set this value automatically.
Heads
The number of read/write heads the disk uses. For older drives, this is the number of physical heads the disk uses. For newer disks, it is the logical number of heads that the drive specifies for use in the BIOS setup, usually 16; see here for an explanation of physical and logical geometry.
For newer drives supported using BIOS geometry translation the BIOS increases the number of heads by the same number it uses to reduce the number of cylinders, so that the number of cylinders is less than the BIOS limit of 1,024.
For example, a Western Digital Caviar 33100 3.1 GB drive has nominal parameters (logical geometry) of 6,136 cylinders, 16 heads and 63 sectors. When you set up this drive (autodetect it) the BIOS will record 767 cylinders, 128 heads and 63 sectors. Of course the drive doesn't really have 128 read/write heads (it doesn't even have 16, only 6), but this is the way that the BIOS gets around the infamous 504 MB restriction. See here for more details on BIOS translation.
Note: Some BIOSes will continue to show the actual physical parameters even when set to a translating mode like LBA. This can be confusing to see on the screen, but if the BIOS is set to "LBA" or "Large", it should be using the translated parameters internally.
Note: IDE autodetection will set this value automatically.
Sectors
This setting is the number of sectors on each track (cylinder and head combination). A sector contains 512 bytes and is the smallest unit of data normally referenced on a hard disk. For older drives that use the same number of sectors per track, this is the number of physical sectors on each track; the most common number is 17.
Newer drives use zoned bit recording to place a different number of sectors on tracks in different parts of the disk. The BIOS only allows a single number for sectors per track (which was kind of bad planning), so these drives use a logical geometry, often specifying 63 sectors per track, the largest number that will fit in this field. The drive translates internally to the correct sector numbers.
Translation Mode
This setting specifies the translation and/or addressing mode for the drive. These special modes are used to enable the BIOS (and operating system) to handle large hard drives and overcome hard disk capacity barriers, especially the infamous 504 binary megabyte / 528 decimal megabyte barrier.
The exact options for this setting will vary by system. These are the ones you are most likely to see:
The BIOS autodetection program will normally take care of making the appropriate mode selection for you (either if you use the "Auto" setting or if you autodetect the drive); in some BIOSes it will only "recommend" the correct mode, but this recommendation is usually accurate. Yet another reason to use autodetection.
Warning: There are a lot of caveats and special rules about how drive translation and addressing works.
Warning: Changing the mode on your hard disk, for example from Large to LBA or
vice-versa, can change the translation method that your BIOS uses for the drive. This can
also happen if you move a drive from a computer that doesn't use LBA to one that does use
it. If the translation mode changes you run the risk of losing all the data on the drive.
It is recommended that you not change translation methods unless there is a specific
reason to do so, and that you back up your data before changing these types of settings in
the BIOS.
Block Mode
When enabled, allows the system to perform accesses to the hard disk in block mode. What this means is that more than one sector can be transferred on each interrupt; newer drives allow you to transfer as many as 16 or 32 sectors at a time. This greatly improves performance when you use multitasking operating systems such as Windows 95 or Windows NT, since the processor is "distracted" from its other work much less often.
Normally you will want to enable this setting if your hard disk is compatible. Disable it if you experience lockups or problems with your hard disk or other peripherals.
Note: IDE autodetection will set this value automatically on most BIOSes, but on some this must be manually set; the autodetection won't do it.
Note: On some BIOSes this setting is actually in the Integrated Peripherals section.
Weird.
PIO Mode
This is the PIO mode setting for the IDE device. IDE/ATA uses one of two different ways to transfer information into and out of memory: either programmed I/O (PIO) or direct memory access (DMA). There are 5 different PIO modes, from 0 to 4, with 4 being the fastest. Newer drives support the faster modes.
You will normally want to select the highest mode that your drive supports. If you experience difficulties you may want to try to drop the mode down to a slower level, but this will impact performance.
Note: IDE autodetection will set this value automatically on most BIOSes, but on some
this must be manually set; the autodetection won't do it.
32-Bit Transfer Mode
Enabling this setting allows for 32-bit data transfers between the processor and the PCI bus. Actual transfers to the disk are always done 16 bits at a time, but enabling this option will cause a small performance improvement on the transfer from the bus to the processor.
If your disk supports this, enable it for a performance increase. Disable it if you encounter any difficulty or if your disk doesn't support it.
Note: This setting has nothing to do with Windows 3.x's "32-bit disk access" or "32-bit file access", which refer to something different entirely.
This section lets you set security passwords to control access to the system at boot time and/or when entering the BIOS setup program. Some systems have a single password, while many newer ones now have two: a supervisor and a user password.
Warning: If you set a password on your system, make sure you write it down in at least two places. If you lose the password you will be locked out of your own system, and then you will have to resort to techniques like these. For most users, a password is unnecessary. In a shared office environment, it can be very helpful however, to control access to the PC.
Supervisor Password
Select this option to set the supervisor password. The supervisor password is the higher level password of the two normally present on the system. On most systems, when the supervisor password has been set, it must be entered in order to access the BIOS setup program, or to change the user password.
User Password
Select this option to set the user password. The user password is the lower level password of the two normally present on the system. The user password usually allows the system to be booted, but does not allow access to the BIOS setup program. The supervisor password must be used to enter the BIOS setup program.
Note: On some systems, either the supervisor or user passwords will allow access to the BIOS setup program. In this case the existence of two passwords may be to allow a single password to be set up for an administrator, which will work for multiple machines, while the user password is individual for each machine.
The newest rage in motherboard design is the so-called "jumperless" motherboard. While this name is an exaggeration--these boards do have jumpers, just fewer of them than a regular motherboard--the idea is sound: to move many of the low-level hardware selection functions from hardware jumpers to regular BIOS settings, accessed through a BIOS settings group sometimes called a "CPU soft menu". Abit has popularized this type of motherboard.
This section describes the settings that are found in this setup group on jumperless motherboards. Regular jumpered motherboards will of course not have a section of this sort in their BIOS setup.
Warning: Setting the values in this section incorrectly can possibly damage your
processor or other hardware.
CPU Name/Type
The BIOS will automatically detect and display the type of CPU in the PC, including the manufacturer and family name (e.g., "Intel Pentium", "AMD K6"). This value cannot be changed.
CPU Operating Speed
This setting allows you to select the operating speed of your processor directly. When you set this value, the BIOS will automatically set the "External Clock" and "Multiplier Factor" values for you, and lock them so they cannot be changed. For example, setting this value to "166" will set the external clock to 66 MHz, and the multiplier to 2.5X. To manually control the external clock and multiplier factor values, you must set this parameter to "User Defined".
External Clock
This setting controls the clock speed of the memory bus on the motherboard, and is normally 50, 60, 66 or 75 MHz. The internal processor speed is the product of the external clock speed of the motherboard and the multiplier used by the processor.
Note: When the CPU Operating Speed parameter is set to a specific number, the External
Clock parameter is computed by the BIOS and this setting is disabled.
Multiplier Factor
This setting controls the multiplier that is used to determine the internal clock speed of the processor relative to the external or motherboard clock speed. The usual values are 1.5X, 2X, 2.5X, 3X, 3.5X and so on.
Note: When the CPU Operating Speed parameter is set to a specific number, the External
Clock parameter is computed by the BIOS and this setting is disabled.
CPU Power Plane
This setting controls how the voltage for the processor is to be specified. There are three different options. Depending on which one you select, the BIOS will change the other available voltage settings:
Plane Voltage
When the CPU Power Plane is set to "Single Voltage", this parameter allows you to choose what the voltage should be. This should be set to the correct voltage for your particular CPU. When CPU Power Plane is set to anything other than "Single Voltage", this setting will not be present.
I/O Plane Voltage
When the CPU Power Plane is set to "Dual Voltage", this parameter allows you to choose what the I/O or external voltage should be. When CPU Power Plane is set to anything other than "Dual Voltage", this setting will not be present.
Core Plane Voltage
When the CPU Power Plane is set to "Dual Voltage", this parameter allows you to choose what the core or internal voltage should be. When CPU Power Plane is set to anything other than "Dual Voltage", this setting will not be present.
CPU Marking
When the CPU Power Plane is set to "Via CPU Marking", this parameter allows you to choose what the marking code is for your CPU, which will tell the BIOS what voltage(s) the CPU requires. You may not know what your code is, or it may not be listed, so you may want to use the manual settings ("Single Voltage" or "Dual Voltage") in this case. When CPU Power Plane is set to anything other than "Via CPU Marking", this setting will not be present.
In addition to the automatic configuration options offered in several specific areas of the BIOS setup (memory timing, hard disk autodetection, etc.) most BIOSes also offer a menu selection to automatically set all options in the BIOS to predefined settings.
Note: Auto configuration selections will not generally replace the settings in the Standard Setup section, in order not to wipe out any specific settings you have entered for your floppy or hard disk drives, or the current date and time.
Warning: It is prudent to record your system's current settings on paper before loading any default settings so that you know what you have changed and can undo the automatic settings if necessary.
Auto Configuration with BIOS Defaults / Failsafe Settings
Select this option to replace most of the current BIOS settings with predefined settings (coded into the BIOS) that are intended to put the system into as stable a state as possible. This means in most cases the slowest memory timings, performance enhancing features turned off, etc. In general, you will want to use this setting if your system becomes unstable after you make many changes, to return it to a known good state.
This will not be an optimal setting in the vast majority of cases; you will want to make modifications after you do this, to improve performance. It is very useful for troubleshooting; if your system doesn't work before you run this and then it does work afterwards, you know that an incorrect BIOS setting was likely your problem.
Auto Configuration with Optimal Settings
Select this option to replace most of the current BIOS settings with predefined settings (coded into the BIOS) that are intended to put the system into what the designers consider an optimal state. You can use this when you first start up your system to get it "close" to what you want it to be when you have made all the changes you feel are necessary for maximum performance. Don't expect these optimal settings to truly be optimal however; the designers can't possibly anticipate how you specifically are going to use your system.
There are generally two ways to exit the BIOS setup program. Most BIOSes have two menu entries that you choose from, to exit either saving your changes, or discarding them. Others exit by hitting the {Esc} key and then ask you if you want to keep changes or discard them.
Save and Exit Setup
Choose this setting to exit the BIOS setup program and save changes to the BIOS CMOS memory. Make sure you select this in order to keep your changes; many times users accidentally forget to do this and then wonder why their system's behavior didn't change even though they modified settings.
Exit Setup Without Saving
Choose this setting to exit the BIOS program discarding all changes made. The BIOS will normally ask for confirmation ("Are you sure?") before exiting. Note that the BIOS program does not keep track of whether or not you actually make changes to any of the settings, the way for example a word processor would, in order to determine if it should warn you. It will warn you every time you tell it to exit without saving.
