With a slower core-processor speed of 233 MHz, the Cyrix MII/300 trailed the Pentium II/300 by 33 percent. Thus we see that Cyrix's PR ratings, which are Intel-equivalent clock speeds instead of the actual speed, hold true for overall system performance but not for CPU performance alone.

You can see the effect of the 100-MHz system bus on the AMD processors when you compare the results of the two K6-2 entries. The K6-2/300, running on a 100-MHz bus, kept pace with the Pentium II/300, while the K6-2/266, running on a 66-MHz bus, lagged behind the Pentium II/266 by 9 percent.

Interestingly, even without the help of 3DNow! instructions built into 3D WinMark core code, the K6-2 chips showed improvements when we enabled the registry to identify 3DNow! processors. That's because 3D WinMark uses DirectX-6 transform and lighting modules, which are 3DNow!-enabled.

By adding a second MMX unit to the K6-2, AMD was able to match Intel's performance. The K6-2/300, with its 100-MHz system bus, came in ahead of the Pentium II/300 on both Photoshop filter tests--the Gaussian Blur test and the Unsharpen Mask test. The K6-2/266 (with a 66-MHz system bus) also beat all the Pentium II units except the 350- and 400-MHz Pentium II CPUs (which have 100-MHz buses) on the Unsharpen Mask test.