Cyrix - PR System

PR System

Because the 6x86 was more efficient on an instructions-per-cycle basis than Intel's Pentium, and because Cyrix sometimes used a faster bus speed than either Intel or AMD, Cyrix and competitor AMD co-developed the controversial PR system in an effort to compare its products more favorably with Intel's. Since a 6x86 running at 133 MHz generally benchmarked slightly faster than a Pentium running at 166 MHz, the 133 MHz 6x86 was marketed as the 6x86-P166+. Legal action from Intel, who objected to the use of the strings "P166" and "P200" in non-Pentium products, led to Cyrix adding the letter "R" to its names.

The PR nomenclature was controversial because while Cyrix's chips generally outperformed Intel's when running productivity applications, on a clock-for-clock basis its chips were slower for floating point operations, so the PR system broke down when running the newest games. Additionally, since the 6x86's price encouraged its use in budget systems, performance could drop even further when compared with Pentium systems that were using faster hard drives, video cards, sound cards, and modems.

Although AMD used the PR rating in its early K5 chips, it soon abandoned the PR rating with the introduction of the K6. However, it would use a similar concept in marketing its later CPUs, starting again with the Athlon XP.