BIOS's and there error codes
During the POST ( Power on self test) routines, which
are performed each time the system is turned on or a hard reset is done
( using the reset switich on the front of the computer). Non-fatal errors
are those which in most cases allow the system to continue the boot up
process. The error messages usually appear on the screen. Fatal errors
are those which halts the boot up and will not let it continue usually
leaving a blank screen and a series of beeps from the computer speaker.
By counting the beeps it enables to track down were the problem is occurring.
Below is a list of beeps codes and error codes for the more common BIOS's,
more will be added as they become available.
AMIBIOS
FATAL ERRORS
No. of Beeps Error Message
1 ------------- Refresh failure-the memory refresh circuitry of the motherboard is faulty.
2 ------------- Parity error-a parity error was detected in the first 64KB of base memory.
3 ------------- Base 64KB memory failure, bad ram or improper type (FPM, EDO)
4 ------------- Timer not operational, Timer #1 on the board has failed.
5 ------------- Processor error, The CPU has generated and error, improper setup or faulty.
6 ------------- Gate A20 Failure, keyboard control by the CPU has failed or is at fault.
7 ------------- Processor Expection Interupt Error,CPU has generated an exception interrupt.
8 ------------- Display Memory Read/Write Error,adapter is missing or faulty,(not always Fatal)
9 ------------- ROM Checksum Error,values in the ROM don't match the values in the BIOS.
10 ------------ CMOS Shutdown Register Read/Write Error, register for the CMOS memory
has failed.
NON - FATAL ERRORS
Non - Fatal Error messages will be displayed to the screen after the
posting, it will tell the error and then usually prompt with: PRESS <
F1> TO RESUME. Most errors of this type are misrepresented values in the
bios that the user has entered by mistake or the invidual peice of hardware
is at fault ( HDD error, Keyboard error, ...). Enter the CMOS configuration
utility by pressing < F1 > or by holding down the < DEL > during
the posting.
AWARD BIOS
With the AWARD BIOS there is only 1 beep code. It consists of 1 long
beep followed by 2 short beeps, this is an indication that a video error
has occurred and the BIOS cannot initialize the video screen to display
any additional information. ALL other errors are displayed on screen. If
there is any other sequence of beeps it will either be a keyboard or ram
error.
PHOENIX
During the posting if there is a fault the BIOS will send a code to
port 80h, some motherboards come with a seven-segment LED display, which
will display the error code, for those not equipped with the display a
"PORT80h" card can be purchased to display the error code which indicates
at what point in the post sequence the fault has occurred. Some faults
are also indicated by a series of beep codes that can range from a single
beep to a sequence of 4 beeps 4 beeps long. A single beep indicates the
computer has entered the posting state, any series of beeps after are the
ones to be noted. If the motherboard makes it past initializing the video
display it will display the error code in the upper left corner of the
display.
Note:
AWARD BIOS and PHOENIX have merged together and more information on
the individual errors can be found at: The AWARD Website
POST Codes
NOTE: EISA POST codes are typically output to port address 300h. ISA POST codes are output to port address 80h.
Code
(hex) Name Description
C0 Turn Off Chipset OEM Specific-Cache control
Cache
1 Processor Test 1 Processor Status (1FLAGS) Verification.
Tests the following processor status flags:
carry, zero, sign, overflow,
The BIOS sets each flag, verifies
they are set, then turns each flag
off and verifies it is off.
2 Processor Test 2 Read/Write/Verify all CPU registers
except SS, SP, and BP with data
pattern FF and 00.
3 Initialize Chips Disable NMI, PIE, AIE, UEI, SQWV
Disable video, parity checking, DMA
Reset math coprocessor
Clear all page registers, CMOS shutdown byte
Initialize timer 0, 1, and 2, including set
EISA timer to a known state
Initialize DMA controllers 0 and 1
Initialize interrupt controllers 0 and 1
Initialize EISA extended registers.
4 Test Memory RAM must be periodically refreshed to
Refresh Toggle keep the memory from decaying. This
function ensures that the memory
refresh function is working properly.
5 Blank video, Keyboard controller initialization.
Initialize
keyboard
6 Reserved
7 Test CMOS Verifies CMOS is working correctly,
Interface and detects bad battery.
Battery Status
BE Chipset Default Program chipset registers with power
Initialization on BIOS defaults.
C1 Memory presence OEM Specific-Test to size on-board
test memory
C5 Early Shadow OEM Specific-Early Shadow enable for
fast boot.
C6 Cache presence External cache size detection
test
8 Setup low memory Early chip set initialization
Memory presence test
OEM chip set routines
Clear low 64K of memory
Test first 64K memory.
9 Early Cache Cyrix CPU initialization
Initialization Cache initialization
A Setup Interrupt Initialize first 120 interrupt
Vector Table vectors with SPURIOUS_INT_HDLR and
initialize
INT 00h-1Fh according to INT_TBL
B Test CMOS RAM Test CMOS RAM Checksum, if bad, or
Checksum insert key pressed, load defaults.
C Initialize Detect type of keyboard controller
keyboard (optional)
Set NUM_LOCK status.
D Initialize Video Detect CPU clock.
Interface Read CMOS location 14h to find out
type of video in use.
Detect and Initialize Video Adapter.
E Test Video Test video memory, write sign-on
Memory message to screen.
Setup shadow RAM - Enable shadow
according to Setup.
F Test DMA BIOS checksum test.
Controller 0 Keyboard detect and initialization
10 Test DMA
Controller 1
11 Test DMA Page Test DMA Page Registers.
Registers
12-13 Reserved
14 Test Timer Test 8254 Timer 0 Counter 2.
Counter 2
15 Test 8259-1 Mask Verify 8259 Channel 1 masked
Bits interrupts by alternately turning off
and on the interrupt lines.
16 Test 8259-2 Mask Verify 8259 Channel 2 masked
Bits interrupts by alternately turning off
and on the interrupt lines.
17 Test Stuck Turn off interrupts then verify no
8259's Interrupt interrupt mask register is on.
Bits
18 Test 8259 Force an interrupt and verify the
Interrupt interrupt occurred.
Functionality
19 Test Stuck NMI Verify NMI can be cleared.
Bits (Parity/IO
Check)
1A Display CPU clock
1B-1E Reserved
1F Set EISA Mode If EISA non-volatile memory checksum
is good, execute EISA initialization.
If not, execute ISA tests an clear
EISA mode flag.
Test EISA Configuration Memory
Integrity (checksum & communication
interface).
20 Enable Slot 0 Initialize slot 0 (System Board).
21-2F Enable Slots Initialize slots 1 through 15.
1-15
30 Size Base and Size base memory from 256K to 640K
Extended Memory and extended memory above 1MB.
31 Test Base and Test base memory from 256K to 640K
Extended Memory and extended memory above 1MB using
various patterns.
NOTE: This test is skipped in EISA
mode and can be skipped with ESC key
in ISA mode.
32 Test EISA If EISA Mode flag is set then test
Extended Memory EISA memory found in slots
initialization.
NOTE: This test is skipped in ISA
mode and can be skipped with ESC key
in EISA mode.
33-3B Reserved
3C Setup Enabled
3D Initialize & Detect if mouse is present,
Install Mouse initialize mouse, install interrupt
vectors.
3E Setup Cache Initialize cache controller.
Controller
3F Reserved
BF Chipset Program chipset registers with Setup
Initialization values
40 Display virus protect disable or
enable
41 Initialize Initialize floppy disk drive
Floppy Drive & controller and any drives.
Controller
42 Initialize Hard initialize hard drive controller and
Drive & any drives.
Controller
43 Detect & Initialize any serial and parallel
Initialize ports (also game port).
Serial/Parallel
Ports
44 Reserved
45 Detect & Initialize math coprocessor.
Initialize Math
Coprocessor
46 Reserved
47 Reserved
48-4D Reserved
4E Manufacturing Reboot if Manufacturing POST Loop pin
POST Loop or is set. Otherwise display any
Display Messages messages (i.e., any non-fatal errors
that were detected during POST) and
enter Setup.
4F Security Check Ask password security (optional).
50 Write CMOS Write all CMOS values back to RAM and
clear screen.
51 Pre-boot Enable Enable parity checker
Enable NMI, Enable cache before boot.
52 Initialize Initialize any option ROMs present
Option ROMs from C8000h to EFFFFh.
NOTE: When FSCAN option is enabled,
ROMs initialize from C8000h to
F7FFFh.
53 Initialize Time Initialize time value in 40h: BIOS
Value area.
60 Setup Virus Setup virus protect according to
Protect Setup
61 Set Boot Speed Set system speed for boot
62 Setup NumLock Setup NumLock status according to
Setup
63 Boot Attempt Set low stack
Boot via INT 19h.
B0 Spurious If interrupt occurs in protected
mode.
B1 Unclaimed NMI If unmasked NMI occurs, display
Press F1 to disable NMI, F2 reboot.
E1-EF Setup Pages E1- Page 1, E2 - Page 2, etc.
FF Boot
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