PR or P-Rating (Performance Rating; often mistaken for "Pentium Rating") was a rating system that allowed various x86 manufacturers to gauge the performance level of their microprocessors against equivalent Pentium-level performance. PR was introduced on February 5, 1996 in a collaborated effort by AMD, IBM, SGS-Thomson, and Cyrix to provide a way to report processor performance.

Measuring P-Rating

Performance rating was obtained by:

1. Obtain a representative target system that supports both the Pentium and Cyrix/IBM/AMD processor (e.g. Am5x86 / K5).
2. Run Winstone 96 using the Pentium Processor and record the scores for the various frequencies.
3. Defragment the hard disk after each test run
4. Replace the Pentium processor with target processor (e.g. Am5x86).
5. Run Winstone 96 using the target processor and record the score for this processor.
6. Compare the Winstone 96 score you get against the Pentium processors. The target processor's P-Rating is based on the highest freqeucny of the Pentium processor that the target processor's Winstone score surpasses.