Editing Cyrix (section)

=== PR system ===

Because the 6x86 was more efficient on an [[Instructions per cycle|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 [[Performance Rating]] (PR) system in an effort to compare their products more favorably with Intel's. Since a 6x86 running at 133&nbsp;MHz generally benchmarked slightly faster than a Pentium running at 166&nbsp;MHz, the 133&nbsp;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 performed more poorly 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 also used the PR numbers for its early [[AMD K5|K5]] chips, it soon abandoned that nomenclature with the introduction of the [[AMD K6|K6]]. However, it would use a similar concept in marketing its later CPUs, starting again with the Athlon XP.