Mac users don't need to talk chips. There are only two major choices in processor chips in all the Macs being sold today. Macs are sold as high-powered or less-powered and priced accordingly.
But the IBM compatible world compares computers by microprocessor chip number. Since chips do most of the computing in a computer, it pays to know a 386SX from a 386.Today's major IBM-type chips belong to three families: 80286, 80386 and 80486. The names are usually shortened to 286, 386 and 486. Until Advanced Micro Devices (AMD) started making them, they were often called i286, i386 and i486. That stood for Intel, who had a near-monopoly. Now we rooters for the small guy have dropped the "i."
The 286 chip is an oldie, as computer technology goes. The 286 is a 16-bit chip. Since it takes 8 bits of data to define a alphabet letter, it can process about two letters at a time.
Judi still uses (and loves) a Dell 286. It does ho-hum jobs like desktop publishing, running databases, heavy numbers juggling and heavy graphics. (Graphics includes design and CAD-CAM work and today's fancy games.) It's plenty fast enough for typing term papers. So if you can get somebody's old IBM AT for under $400 for your schoolkid, it may be a very good buy.
Today's high-powered computers use a 386 or 486 chip. They're also called 386DX and 486DX. Both process 32 bits of data at a time, twice as fast as the 286.
The 486 is nearly identical to the slightly older 386, except for four additions.
For one, it has a built-in math coprocessor. People who do a lot of work with graphics and raw numbers will notice the speed. But it often costs about $3,000 more than a 386. Since an add-on math coprocessor chip (80387) at $1,000 list gives us almost as much speed on the 386, why opt for the 486?
Here's another selling point: The 486 has an 8K cache to store some data. Theoretically, that keeps it working when a 386 might be waiting to move data. But we can get an add-on 128K cache for our 386 for $600 retail.
Here's a third selling point: The 486 can theoretically process data at clock speeds over 40MHz. (We'll talk more later about clocks.) Ah, but manufacturers can't yet make the chip perform reliably at such high speed. Until they do, the newer chip better have a lot more going for it.
Fourth point: Intel's 486 has improved internal circuits that make it process data a trifle faster than Intel's 386. That's not surprising. Every time a computer company re-engineers a part, it gets better.
However, when AMD completely re-engineered the i386 to make its 386 (made necessary by copyright conflicts), AMD came up with a 386 chip that processes data a trifle faster than Intel's 486. Alas, only the rare computermaker lets buyers know if it's using Intel, AMD or some other knockoff chip.
There's more to the chip story. Chipmakers did some funny things after they designed 386 and 486 chips. They crippled some of the parts.
The crippled versions have `SX' after their names. The 486SX is a 486 with a disabled math coprocessor. As we said, you can add that.
Intel's 386SX can't take in and spit out 32 bits of data at one time (while, like the 386, it can still process 32 bits in a gulp). It only moves 16 bits at a pass on its data bus. (The bus is the set of conductors or wires that moves data between the chip and the rest of the computer.) That makes it slower at graphics, games, heavy-duty spreadsheeting and similar activities.
Here's a rule to remember: It almost never pays to buy a computer with a 386 or 486 chip unless its bus can move 32 bits at a time. Any DX computer with only a 16-bit data bus (often called AT-compatible or ISA for Industry Standard Architecture) might as well use a 386SX chip.
But here's more confusion: EISA buses are 32-bit buses. Some MCA buses are not.
It costs a bit more to make SX than DX chips. Yet machines built on SXs sell for less! That's because SXs are priced at regular make-'em-and-mark-'em-up levels. In our opinion, DXs (even those that aren't noticeably better than SX equivalents) sell at make-'em-andgouge-'em prices.
If two computers use the same chip, watch the clock. There's a quartz clock in every computer. Each clock tick tells the chip to perform one function. So faster clock speeds convert directly to faster data processing.
Clock speeds are measured in megahertz (MHz), millions of ticks per second, and usually listed right after the chip number. A 386/33MHz computer is significantly faster than a 386/25. But a 486/33 is only a little faster than a 386/33, except when crunching raw numbers or graphics (which both get processed by the uncrippled math module in the 486 chip).
Know who rates a chip for clock speed? The maker's quality control people. At the end of each chip assembly line, quality control tests the chips running at 50MHz. The few that can run that fast get labeled and sold for use with a 50MHz clock. The rest get tested at 33MHz. Those that pass get labeled for 33MHz use. The rest get tested for 25MHz use. Nowadays, any that don't pass are junked.
Why do faster-running machines cost so much more? Because people will pay so much more.