The computer is full of chips. Let’s examine them.

 

If you unscrew the system unit (the box containing the CPU and memory) and peek at the circuitry inside, you’ll see a green plastic board, on which is printed an electrical wiring diagram.

Since the diagram’s printed in copper (instead of ink), the diagram conducts electricity. It isn’t just a diagram of an electrical circuit; it is an electrical circuit!

The green plastic board — including the circuit printed on it — is called a printed-circuit board (PC board). Each wire that’s stamped onto the PC board is called a trace.

The typical computer contains several PC boards.

Motherboard & babies

In your computer, the largest and most important PC board is called the motherboard (or, more briefly, mobo).

The other PC boards are smaller. Those little baby boards (about the size of a postcard) are called PC cards.

The typical motherboard has several slots on it. Into each slot, you can put a PC card.

Caterpillars

On each PC board, you’ll see black rectangles. If you look closely at a black rectangle, you’ll see it has tiny legs, so it looks like a black caterpillar.

The “caterpillars” come in many sizes. In a typical computer, the shortest caterpillars are ¾ of an inch long and have 7 pairs of legs; the longest are 2 inches long and have more legs.

Though each black caterpillar has legs, it doesn’t move. It’s permanently mounted on the PC board.

Each leg is made of tin and called a pin.

Hidden inside the caterpillar is a metal square, called a chip, which is very tiny. The typical chip is just an eighth of an inch long, an eighth of an inch wide, and a hundredth of an inch thick! On that tiny metal chip are etched thousands of microscopic electronic circuits! Since all those circuits are on the chip, the chip’s called an integrated circuit (IC).

4 purposes

Each chip serves a purpose.

So a chip is either a processor chip, a memory chip, an interface chip, or a support chip — or it’s a combination chip that accomplishes several purposes.

How chips are designed

To design a chip, the manufacturer hires an artist, who draws on paper a big sketch of what circuits to put onto the chip. It helps if the artist also has a degree in engineering — and knows how to use another computer to help draw all the lines.

After the big sketch is drawn, it’s photographed.

Buying chips

If you ask a computer dealer to sell you a chip, the dealer also gives you the chip’s DIP (the entire caterpillar).

Since you’ve asked for a chip but also received a DIP, you might think the caterpillar (the DIP) is the chip. But the caterpillar’s not the chip; the chip hides inside the caterpillar.

The typical caterpillar-and-chip costs $3, but you might pay a different amount, depending on how fancy the chip’s circuitry is.

You can get chips mail-order from JDR Computer Devices in California, phone 800-538-5000 or 650-625-1400.

How chips chat

The chip inside the caterpillar acts as the caterpillar’s brain. The caterpillar also contains a “nervous system”, made of thin wires that run from the brain (the chip) to the legs (the pins). The wires in the caterpillar’s nervous system are very thin: each wire’s diameter is about half of a thousandth of an inch.

If one caterpillar wants to send electrical signals to another caterpillar, the signals go from the first caterpillar’s brain (chip) through the caterpillar’s nervous system to its legs (pins). Each pin is attached to a trace (wire) on the PC board. The signals travel through those traces, which carry the signals across the PC board until the signals reach the second caterpillar’s pins. Then the signals travel through the second caterpillar’s nervous system to that caterpillar’s brain (chip).

Binary code

To communicate with each other, the caterpillars use a secret code. Each code is a series of 1’s and 0’s. For example, the code for the letter A is 01000001; the code for B is 01000010; the code for the number 5 is 101; the code for 6 is 110.

That’s called the binary code, because each digit in the code has just two possibilities: it’s either a 1 or a 0. In the code, each 1 or 0 is called a binary digit. A binary digit is called a bit. So in the computer, each bit is a 1 or a 0.

When a caterpillar wants to send a message to another caterpillar, it sends the message in binary code.

The speed at which bits are sent is measured in
bits per second (bps).

 

The computer system contains memory chips, which remember what problem the CPU (the computer’s brain) is working on.

You want 3 kinds of memory chips: RAM, ROM, and
flash memory.

Let’s begin by looking at RAM chips.

If a chip remembers info just temporarily, it’s called a random-access memory chip (RAM chip). When you buy RAM chips, they contain no info yet; you tell the CPU what info to put into them. Later, you can make the CPU erase that info and insert new info instead. The RAM chips hold info just temporarily: when you turn the computer’s power off, the RAM chips are automatically erased.

Whenever the CPU tries to solve a problem, the CPU stores the problem in the RAM chips, temporarily. There it also stores all instructions on how to solve the problem; the instructions are called the program.

If the computer doesn’t have enough RAM chips to hold an entire problem or program, you (or a programmer) must split the problem or program into several shorter ones instead and tell the CPU to work on each short problem temporarily.

How RAM is measured

A character is any symbol you can type on the keyboard, such as a letter or digit or punctuation mark or blank space. Examples:

Instead of saying “character”, hungry programmers say byte. So the phrase LOVE 2 KISS U consists of 13 bytes. If you store that phrase in the RAM, that phrase occupies 13 bytes of the RAM.

To honor the words “kilobyte”, “megabyte”, “gigabyte”, and “terabyte”, programmers name their dogs Killer Byte, Make A Byte, Giggle Byte, and Terror Byte.

Rows of RAM chips

In a primitive old microcomputer (such as the Commodore 64), the RAM is a row of eight chips on the motherboard. That row of chips holds a total of 64 kilobytes (64K). That row of chips is called a 64K chip set. Each chip in that set is called a “64K chip”, but you need a whole row of those 64K chips to produce a 64K RAM.

If your computer has very little RAM, you can try to enlarge the RAM by adding extra rows of RAM chips to the motherboard. But if the motherboard’s already full, you must buy an extra PC card to put the extra chips on. That extra PC card is called a
RAM memory card.

Parity chip

The original IBM PC contained an extra chip in each row, so each row contained 9 chips instead of 8. The row’s ninth chip is called the parity chip. It double-checks the work done by the other 8 chips, to make sure they’re all working correctly!

So for an original IBM PC (or imitations of it), you must buy 9 chips to fill a row.

RAM sticks

If your computer is modern and you want to insert an extra row of RAM chips, you do not have to insert 8 or 9 separate chips into the motherboard. Instead, you can buy a RAM stick (tiny memory card) that contains all 8 or 9 chips and just pop the whole strip into the computer’s motherboard, in one blow.

Some computers use SIMMs containing a set of just 2, 3, or 4 chips. That set of special chips imitates 8 or 9 normal chips.

A nanosecond is a billionth of a second. The typical SIMM contains chips that are fast: they retrieve info in 60 nanoseconds. Some SIMMs and DIMMs contain chips that are even faster: 10 nanoseconds.

Dynamic versus static

A RAM chip is either dynamic or static.

If it’s dynamic, it stores data for just 64 milliseconds. After the 64 milliseconds, the electrical charges that represent the data dissipate and become too weak to detect.

If a chip is static instead of dynamic, the electrical charge never dissipates, so you don’t need a refresh circuit. (But you must still keep the power turned on.)

In the past, computer designers used just static RAM because they feared dynamic RAM’s refresh circuit wouldn’t work. But now refresh circuits are reliable, and the most popular kind of RAM is dynamic.

Dynamic RAM is called DRAM (pronounced “dee ram”). Static RAM is called SRAM (pronounced “ess ram”).

Faster circuitry

The circuitry on SIMM and DIMM cards has improved, to let a stream of data get from the memory card to the CPU chip faster. Such improvements have fancy names:

If you want to buy an extra SIMM or DIMM to put in your computer, make sure you buy the same kind already in your computer.

How much RAM?

The original IBM PC came with just 16K of RAM, but you could add extra RAM to it. To run modern Windows software, you need at least 4 gigabytes of RAM.

Prices

If you tell HP to custom-build a computer for you, HP typically charges $10 per extra gigabyte of RAM. For example:

But to switch from 16G of DDR4 SRAM to 32G, add just $110 (not $160).

 

If a chip remembers info permanently, it’s called a read-only memory chip (ROM chip), because you can read the info but can’t change it. The ROM chip contains permanent, eternal truths and facts put there by the manufacturer, and it remembers that info forever, even if you turn off the power.

Here’s the difference between RAM and ROM:

A traditional computer includes many RAM chips (arranged in rows) but just a few ROM chips.

What kind of info is in ROM?

In a traditional computer, one of the ROM chips contains instructions that tell the CPU what to do first when you turn the power on. Those instructions are called the ROM bootstrap, because they help the computer system start itself going and “pull itself up by its own bootstraps”.

In a traditional computer, that ROM chip also contains instructions that help the CPU transfer information from the keyboard to the screen and printer. Those instructions are called the ROM operating system or the ROM basic input-output system (ROM BIOS).

How ROM chips are made

The info in a ROM chip is said to be burned into the chip. To burn in the info, the manufacturer can use two methods.

One method is to burn the info into the ROM chip while the chip’s being made. A ROM chip produced by that method is called a custom ROM chip.

An alternate method is to make a ROM chip that contains no info but can be fed info later. Such a ROM chip is called a programmable ROM chip (PROM). To feed it info later, you attach it to a device called a PROM burner, which copies info from a RAM to the PROM.

Info burned into the PROM can’t be erased, unless the PROM’s a special kind: an erasable PROM (EPROM). You can buy 3 types of erasable PROMs:

After you erase an erasable PROM, you can feed it new info.

Electronic devices (smartphones, tablets, laptops, and desktops) now tend to include flash memory instead of old-fashioned ROM, because flash memory is more flexible: it can be upgraded more easily whenever software improvements are needed.

 

The part of the computer that thinks (“the brain”) is called the processor (or central processing unit or CPU).

In a maxicomputer or minicomputer, the processor consists of several chips, which are processor chips.

In a microcomputer, the processor is so small it consists of just a single chip, called a microprocessor. It sits on the motherboard. Yes, in a typical microcomputer, the part that does all the thinking is just a tiny square of metal, less than ¼" on each side!

Intel’s designs

The typical microprocessor uses a design invented by Intel. Intel has gradually improved that design by putting more circuitry on the chip:

The Intel Pentium could have been called the “Intel 586”, but Intel called it the “Pentium” instead so Intel could trademark the name and prevent companies from copying it. It’s the first computer chip that sounds like a breakfast cereal: “Hey, kids, to put zip into your life, try Penti-yumms. They build strong computer bodies, 5 ways!”

Gigahertz

In an army, when soldiers march, they’re kept in step by a drill sergeant who yells out, rhythmically, “Hup, two, three, four! Hup, two, three, four! Hup, two, three, four!”

Like a soldier, the microprocessor takes the next step in obeying your program just when told by the computer’s “drill sergeant”, which is called the computer clock. The clock rhythmically sends out a pulse of electricity; each time the clock sends out a pulse, the microprocessor does one more step in obeying your program.

The clock sends out billions of pulses every second, so the microprocessor accomplishes billions of steps in your program every second!

Each pulse is called a clock cycle. The clock’s speed is measured in cycles per seconds. A “cycle per second” is called a hertz (Hz), to honor German physicist Heinrich Hertz.

Slower than a Pentium

The Pentium’s an amazing chip: while it thinks about one part of your program, it simultaneously starts getting the next part of your program ready for processing. That chip’s ability to do several things simultaneously is called parallel processing.

The Pentium is smarter than old chips (the 8088, 286, 386, and 486): the Pentium can perform more tasks simultaneously; it performs more parallel processing.

Variant chips

Old chips had variants:

The Pentium comes in many versions. Here are the most popular, listed from slowest to fastest:

To help low-income folks, Intel eventually decided to make a cheaper Pentium, called Celeron. It goes slower.

For very low-income folks, Intel makes a version that’s even cheaper & slower, called the Atom.

What’s available

Intel stopped marketing the oldest chips (8086, 8088, 286, 386, 486 and oldest Pentiums). Modern computers use these new Pentiums: the Core i3, Core i5, Core i7, and Core i9.

Here are prices of various Pentium chips:

That chart shows the lowest price charged by resellers for a single chip in June 2021, according to Intel. By the time you read this, prices might be lower, since prices change frequently (about every 2 months). That chart also shows how much cache memory (fast-access internal memory) is included inside the Pentium chip.

If you tell HP to custom-build a computer for you, here’s what HP charges:

 

Imitations

Intel’s competitors imitate Intel’s chips. For example, these imitations go faster than Intel’s originals:

Advanced Micro Devices (AMD) makes Ryzen chips, which compete against Intel’s Pentium Core chips:

That chart shows the price charged for a single chip in January 2021, according to Wikipedia.

Half-assed systems

While a chip waits for your commands, the chip accomplishes nothing useful during the wait: it just mumbles to itself.

Total cost

When you buy a computer, its advertised price includes a microprocessor, motherboard, and other goodies. Pay for the microprocessor separately just if you’re inventing your own computer, buying parts for a broken computer, or upgrading your computer by switching to a faster microprocessor & motherboard.

Though the microprocessor is cheap, the computer containing it can cost many hundreds or thousands of dollars. That’s because the microprocessor is just a tiny part of the computer. In addition to the microprocessor, you’ll want memory chips, interface chips, support chips, PC boards (to put the chips on), I/O devices (a keyboard, screen, printer, speaker, and mouse), disks, and software.

Math coprocessor

Each Pentium chip includes math coprocessor circuitry, which handles advanced math fast. That circuitry can multiply & divide long numbers & decimals and compute square roots, logarithms, and trigonometry.

Primitive chips — the 8088, 8086, 286, 386SX, 386DX, and 486SX — do not include such circuitry.

Here’s the only difference between a 486DX chip and a 486SX chip:

If your CPU lacks math-coprocessor circuitry (because your CPU is an 8088, 8086, 286, 386, or 486SX), here’s how to do math quickly: buy a math coprocessor chip. Put it next to the CPU chip on the motherboard. It contains the math-coprocessor circuitry that the CPU lacks.

Better yet, give up and buy a new computer, containing a Pentium!