Classic Computer Magazine Archive COMPUTE! ISSUE 158 / NOVEMBER 1993 / PAGE 128

Cyrix Cx486DRx2. (replacement microprocessor) (Hardware Review) (Evaluation)
by David English

It's no fun owning a 386 anymore. With today's more powerful software, 386 machines feel slow. You could sell your 386 and buy a new 486, or you could buy a new 486 motherboard and swap out your old one. But there's a third solution that's much less complicated.

Cyrix has a single-chip upgrade that can bring 486-level performance to your 16-MHz, 20-MHz, or 25-MHz 386DX system. All you do is pull out your old CPU (a chip puller is included), put the new Cx486DR[x.sup.2] chip in its place, install the heat sink on top of the chip (20-MHz and 25-MHz upgrades only), and install the cache software (which simply turns on the processor's cache; it doesn't take up any memory).

The new chip speeds up your computer in three ways. First, it acts as a clock doubler, so your 16-MHz machine will run at 32 MHz, your 20-MHz machine will run at 40 MHz, or your 25-MHz machine will run at 50 MHz. Second, the chip includes a built-in 1K cache, which isn't found on 386 chips. (A true 486 has a built-in 8K cache, which gives it a greater advantage in this area.) Finally, the Cx486DR[x.sup.2] has an instruction set that's compatible with Intel's 486 instruction set. According to Cyrix, all DOS, Windows, and OS/2 software will work with its upgrade chip.

The upgrade chip doesn't include a math coprocessor (which the 486DX has, but the 486SX doesn't have). However, it is compatible with Intel's 387 math coprocessors and Cyrix's own FasMath 83D87 math coprocessor.

I tested a Cx486DR[x.sup.2] 20/40 chip on a four-year-old ZEOS 386DX system. Before I installed the Cyrix chip, Norton Utilities showed an Intel 20-MHz 386DX with a speed of 8.9. After the installation, Norton showed a Cyrix 40-MHz 486 with a speed of 47.9. With the 386DX, WindSock reported speeds of CPU: 85, Video: 37, Disk: 82, Memory: 35, and Overall: 70. With the 486DR[x.sup.2], WindSock reported CPU: 268, Video: 86, Disk: 113, Memory: 35, and Overall: 160.

As you can see from the WindSock numbers, a faster processor can even accelerate your system's video and hard drive performance. Short of buying a new motherboard or a new computer, getting the Cyrix 486 upgrade chip is the best way to speed things up.