How to speed up your PC's performance, Part II

HOME COMPUTING

August 31, 1992

Writing a computer column is a bit like being married. If you forget something important, you're going to find out about it right away.

So to the people who called and wrote to complain of things I didn't mention in my column on buying a fast computer, my apologies. The problem, as always, is space. I get more than most columnists, but there never seems to be enough.

This time, we'll talk about a few of the items I left off the fast-computer list -- items that can make quite a difference in your machine's performance under the loads of today's demanding software and graphical operating environments.

Last time, I noted that the overall speed of a system depends on the type of microprocessor, the computer's internal clock rate, the amount of memory available and the speed of your computer's disk drive.

But there are several ways to boost memory and disk performance under any environment. Some may add a bit to the cost of your computer. Others may be sitting unused on your hard disk right now.

One of the best ways to speed up an IBM-compatible computer is through memory and disk caching.

The generic definition of cache (pronounced "cash") is a temporary storage area, usually located away from one's main place of operation and close to the job at hand.

Memory and disk caches set up temporary data storage areas, under the theory that the next piece of information your program asks for will be located somewhere near the last piece of information it got.

Many of the better IBM-compatibles today come with cache memory controllers. These contain a small amount of high-speed static RAM, ranging from 64K to 256K, that operates much faster than your computer's main memory.

When your program asks the computer to fetch information from a particular memory location, it will actually read in a much larger chunk of information from your computer's main memory area and put it in the high-speed memory cache.

If the next piece of information the computer needs is in the high-speed cache, your computer can retrieve the data much faster than if it had to go back to the main memory.

nTC A memory cache is something you'll have to buy with your computer. I don't know anyone who ever installed one afterward. If the computer you're considering has a cache controller, the advertisement or display will say so.

Intel's 80486 microprocessor comes with its own internal 8K cache, which is one of the reasons why 486 computers are faster than earlier 80386 machines running at similar speeds. But even a 486 will benefit from an external cache.

How big a cache you need is a matter of debate. Most experts consider a 64K cache minimal, but there's debate about whether a 256K cache will give you much better performance than 128K. No matter what the size, any cache is better than none. You'll pay a little more for a memory cache, but the performance boost is often worth it.

Unlike memory caches, disk caches can be created in hardware or software. They work basically the same way as memory caches. When your program asks for a chunk of data from your disk drive, a caching disk controller or caching software will read in a much larger chunk of data and store it in memory.

If the next piece of data your program would normally get from the disk is already in the cache, your computer will get it there, eliminating the need for another slow trip to the disk drive.

There are ways to boost memory and disk performance. Some may add a bit to the cost of your computer. Others may be sitting unused on your hard disk.

Some expensive hard-disk controllers, designed for use on file servers that provide storage for computer networks, have hardware caches built in.

You'll pay a substantial premium for a caching disk controller (and you'll rarely find them on standard machines designed for home or office use). But you can get almost the same performance increase through software that uses your computer's extended memory as a disk cache (another reason for buying as much memory as you can afford).

You can buy a stand-alone caching program, such as PC-KWIK, or use the SmartDrive program that comes packaged with the latest versions of Microsoft's Disk Operating System (DOS). Another trick for speeding up disk access is a program that comes with DOS that can turn extended memory into what your computer thinks is another disk drive. Files copied to a RAM disk, as it's known, can be accessed much faster than files on the drive itself.

A combination of disk caching software and a RAM disk can virtually double the speed of many programs running under Microsoft Windows -- and the software to set them up is already on your disk.

If you're into large, complex spreadsheets, or you use design software that requires complex calculations, a math coprocessor can speed things up by an order of magnitude.

A math coprocessor frees your main processor from performing computational chores. Intel 80486 chips have a math coprocessor built in, but plug-in coprocessors are available for computers using earlier-generation 80386, 80286 and 8086 processors.

Finally, if you're running Microsoft Windows and you're getting tired of waiting for the screen to redraw, consider one of the new so-called "accelerator" video boards designed especially for Windows.

Like math coprocessors, these boards have chips that take over the burden of drawing all the lines, circles and patterns that graphic environments require, freeing up the main processor for other jobs.

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