Performance rating

The PR (Performance Rating) system was a figure of merit developed by AMD and Cyrix in the mid-1990s as a method of comparing their x86 processors to those of rival Intel.

The first use of the PR system was in 1996, when AMD used it to assert that their AMD 5x86 processor was as fast as a Pentium running at 75 MHz. The designation "P75" was added to the chip to denote this.

The letters PR stood for "Performance Rating", but many people mistakenly thought it stood for "Pentium Rating", as the PR was often used to measure performance against Intel's Pentium processor.

Later that year, Cyrix also adopted the PR system for its 6x86 and 6x86MX line of processors. These processors were capable of handling business applications under Microsoft Windows faster than Pentiums of the same clock speed, so Cyrix PR-rated the chips one or two Pentium speed grades higher than clock speed. AMD did likewise with some versions of their K5 processor, but abandoned the system when it introduced the K6.

The PR system drew criticism, being based on a limited set of benchmark suites which measured only integer performance, a strong point of the K5 and the 6x86 in particular. Experts argued that this made the PR-rated chips poor choices for games, streaming video, or encoding MP3 music.

However, for integer-intensive tasks which were more commonplace at the time, such as word-processing, spreadsheet editing and web browsing, the substantially lower cost of the PR-rated processors allowed the user to afford a higher-spec part. With the demise of the Cyrix MII (a renamed 6x86MX) from the market in 1999, the PR system appeared to be dead, but AMD revived it in 2001 with the introduction of its Athlon XP line of processors.

...
Wikipedia