Playing alphabet soup helps to devour PC data


Time to play alphabet soup again.

What, you've never heard of the game? Then you've obviously never ventured into the personal computer market, where manufacturers and technofreaks square off every day in an escalating and mind-numbing battle of acronyms and number jumbles designed to reduce the average human to a mound of babbling jelly.

Judging from the questions I get from new computer buyers, and even those upgrading from systems they bought in the mid-80's, today's alphabet soup is a pretty murky brew, full of DX's and SX's and other terms that nobody paid much attention to until recently.

But if you don't pay attention now, you can wind up buying a lot less computer than you really want, or a lot more than you need. So we'll learn about those "X" words. They're actually one of three alphabet soup ingredients that make up the generic name of any IBM-compatible computer.

The first part of the name is actually a string of numbers that tells you what kind of microprocessor is in the computer.

The processor is the heart of the machine, like the engine of a car. Virtually all IBM-compatibles on the market use variants of Intel's 80386 or 80486 microprocessor chips. These are more commonly referred to as 386 or 486 machines.

The 486 is a newer and more powerful engine than the 386, just as a V-8 is more powerful than a V-6. While other factors affect a computer's speed, a 486 chip generally will run programs much faster than a 386, which is important if you're using Microsoft Windows or other graphics-intensive software.

Until 18 months ago, 386 machines were pretty hot stuff, and 486 machines were strictly for power-trippers with deep pockets. But when other manufacturers learned to clone the 386 chip, Intel chopped the price of its 486 line dramatically. As a result, many manufacturers are dropping 386 computers, or selling them as bargain-basement machines in discount warehouses and office supply stores.

DX and SX are terms Intel coined to describe subspecies of its 386 and 486 lines. The 80386DX is the real McCoy. In the trade, it's known as a full 32-bit chip, a term that describes the size and complexity of instructions it can handle, as well as the width of the data highway it uses to communicate with other parts of the system.

The 386SX, on the other hand, is a cheaper version of the 386 chip. It has the same 32-bit internal architecture, but communicates with the rest of the world with a 16-bit data highway, as Intel's earlier and less powerful chips did.

Generally, 386SX chips will run a bit more slowly than 386DX chips with the same clock speed. Technically, it's also possible to design software that will run on a 386DX but not on an SX. But software publishers haven't done that yet.

The 386SX is found in many of today's low-end computers, but if you're trying to run Microsoft Windows, it's no bargain.

With the 486 chip, DX and SX take on a different meaning. The 486DX is really a beefed-up 386 with an on-board math coprocessor and an internal high-speed memory cache, both of which give the 486 a substantial speed advantage over the 386.

The math coprocessor can make any math-intensive program run faster by taking the computational load off the main processor. Spreadsheets and drawing programs benefit most from it. If you're using a computer strictly for word processing, it doesn't matter much.

The 486SX is essentially a DX chip without the math co-processor. While critics describe it as a V-8 engine that only runs on six cylinders, it's a cheaper alternative to the DX without sacrificing much power for basic tasks such as word processing.

Now to the third part of the name -- the speed of the chip. This is a number that represents the speed of the internal clock that governs the computer system. It's expressed in millions of cycles per second, or Mhz. Faster is always better.

Computers with 386SX chips generally run at 25 Mhz. You'll see them advertised as 386SX/25 machines. Some older models and a few laptop computers run at 16 or 20 Mhz. Don't try to run Microsoft Windows on one of these unless you have a lot of patience.

Machines based on the 80386DX chip generally run at 33 or 40 Mhz. Machines with 386DX/33 processors are still powerful enough for many users, even those running Windows, although the drop in 486 prices has made the older designs much less of a bargain than they were.

The newer 486 chips come in a variety of speed ranges. The 486SX/25 has become very popular because it delivers a lot of bang for the buck.

Typically these 486SX computers run $200 to $300 more than 386 models but are several hundred dollars cheaper than 486DX machines. IBM is selling some nicely equipped 486SX/25 packages for as low as $1,600.

If you're going all the way to a 486DX (which is my recommendation unless you're really counting pennies), you'll find 33, 50 and DX/2 66 Mhz computers. The 66 Mhz DX/2 is a little wrinkle Intel added to double the internal speed of the chip while the rest of the system runs at 33 Mhz

While the 50 and 66 Mhz chips theoretically run faster than 33 Mhz models, at this end of the power curve other factors such as your disk drive controller and video board can have more impact on the speed of sophisticated graphics and desktop publishing programs.

So what do you buy? If you're running Word Perfect under DOS and don't expect to do anything but that, a 386SX/25 will do just fine. But if you're interested in running Microsoft Windows or other graphics intensive programs, a 486SX/25 or 486DX/33 is your best bet.

(Michael J. Himowitz is a columnist for The Baltimore Sun.)

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