The PR (performance rating, P-rating, or Pentium rating) system was a figure of merit developed by AMD, Cyrix, IBM Microelectronics and SGS-Thomson in the mid-1990s as a method of comparing their x86 processors to those of rival Intel.
[3]: 3 Later that year, Cyrix also adopted the PR system for its 6x86[1] and 6x86MX line of processors.
The efficient Athlon XP chips could perform better than similarly-clocked chips from Intel's competing Pentium 4 line-up, which depended on high clock speeds to overcome their low IPC.
[3]: 6 Maximum PC criticized this as making it more difficult for power users to differentiate between the various Athlon XP chips.
For example, two chips could be given the same "PR" branding but have much different engineering (cache size, bus speed, etc), which would affect their performance at different tasks.