Classic Computer Magazine Archive COMPUTE! ISSUE 168 / SEPTEMBER 1994 / PAGE 50

How to upgrade your PC's processor. (Compute's Getting Started With: Upgrading Your PC)(personal computer)
by Richard O. Mann

One way to drag your old hardware out to the leading edge of technology is to pop. out its outmoded old horse-and-buggy-days CPU (Central Processing Unit - the brain of the computer) and slide in a new chip. A 486DX4-100 sounds good or maybe a Pentium, right?

For some, it's almost that easy; for others, the whole chip upgrade scenario can become a nightmare. Yet others can forget it entirely; their aging computers weren't built to allow upgrades. Most of us fall somewhere in between.

Can I Upgrade My


The first step is to determine if a chip upgrade is even possible. Many of the larger clone makers purposely make their computers nonstandard enough to force you to buy upgrade components directly from them - at prices well above street prices for normal upgrade hardware. Packard Bell, Leading Edge, Epson, and Hyundai fall into this group.

Other clones tend to be more standard, but the only way to be sure is to talk to your computer vendor (or perhaps the upgrade chip vendor) to see if your particular machine is capable of accepting an upgrade chip. (This advice applies to motherboards, as well.)

If you have a 486SX or DX running at 16, 25, or 33 MHz, you're in luck. Upgrading these newer chips is usually much easier than upgrading earlier CPUs - the upgrade fever had hit before these machines were made, and manufacturers often made allowances for upgrades.

How Far Should I


Once you know you can upgrade your chip, the next question is how far into the future to go. Two factors will determine this: price and desired performance boost Price, of course, is a judgment call that only you can make. Note, however, that competition from Cyrix and AMD has brought the price of all 486 chips down rapidly, making the upgrade route more attractive than ever.

Considering the performance boost you'll get from the various chips available is a little more of a challenge. Remembering the bottleneck analysis mentioned above, you may put a speed demon chip in your computer without much effect - because of other speed-limiting components of your system. With a slow hard drive and a 16-bit bus, for instance, the fastest chip may still take long minutes to load Windows.

You need to balance the chip's speed with the capabilities of the rest of your computer. A Pentium OverDrive chip in a slot where a 486SX-25 once held court would still be limited by the 25-MHz bus moving only 32 bits of data at a time. You'd be missing out entirely on one of the major advantages of the Pentium - its 64-bit bus, It would still be faster than the old chip, of course, but not as fast as it could be.

If you're not comfortable with discussions of bus width (16 bits, 32 bits, or 64 bits) and bus speed (16 MHz, 25 MHz, or 33 MHz), you may need to find a helpful dealer who can tell you how the new chip will perform with your existing setup.

At this writing, Pentium upgrade chips for the OverDrive sockets found in many computers manufactured since mid 1992 are still not available. Code-named P24T, the chip uses Pentium technology inside (including a 64-bit data bus) but communicates with the outside world through the 32-bit bus that exists in 486 systems. Early tests with the first P24T chips found that they not only didn't work in some computers but actually destroyed them. Following many delays, Intel now promises the Pentium OverDrive chip by the end of the year.

In the meantime, Intel has released the clocktripled 486DX4-75 and 486DX4-100 chips, which communicate with the computers at 25 MHz and 33 MHz respectively, while operating internally at the previously unheard-of speeds of 75 and 100 MHz. According to Intel, these chips deliver entry-level Pentium speed.

Installing a Now Chip

For some, installing a new chip is as easy as removing the old chip and plugging in a new one. For others, it can be an experience on a par with root canal work.

Removing the old chip is often easier said than done. Upgrade kits usually supply a many-toothed chip-puller tool that allows you to gently work the nearly two hundred pins of the old chip out of their sockets. If the computer was well designed, you'll have access to the chip area to do this. In too many cases, though, the chip is hidden under a halfdozen other components that you'll have to remove to get at the chip. In some cases, it's nestled into a secure home covered by a nonremovable part of the casing.

Wherever it is, it has to come out before you can put in the new one - unless you have one of the newer computers with a separate upgrade socket.

Installing the new chip must be done with exquisite care. You don't want to bend or break one of its scores of pins - the little legs that must fit precisely into their proper holes in the socket, Considering the cost of this little bit of silicon and metal, you want to be very, very careful as you ease it into its new home. Be sure it's seated securely in the socket before applying power.

Flip the power switch, listen for frying noises, and watch for smoke. Absent smoke and flame, you've probably done it right. If the power switch sets off your own little electrical storm - well, you really should have opted for a new system anyway, right?

Seriously, you should be moderately confident of your ability to work with these precious components before tackling a job where mistakes are so costly. But if you exercise appropriate caution and follow the directions, you'll usually come out of the experience with new confidence and a wonderfully souped-up, like-new PC.