Can anybody tell me where the Performance Rating for the CPU is derived from in SiSoft's Sandra program ? I have used this application in the past and it has always reported a PR equal to or a couple of Mhz more than the official rating of the CPU. However, I have just bought an 1Ghz Athlon PC and Sandra is giving a PR of 1336. Does this mean that it has been benchtested by AMD at this speed ? Is the result burnt into the chip somehow. Could I safely overclock my CPU to some value under this rating ? eg 1200Mhz.

I don't think it works like that. My 1.33 @ 1.55g Tbird has a pr of 2063. I'm courious also what the hell that means.

The PR rating was a rating used creatively by Cyrix in order to better represent their earlier processors. For instance, the Cyrix PR 166 was not a 166mhz processor, it was a 150 (or maybe 133) but they gave it a PR rating of 166 because they maintained that the CPU had comparable performance to a Pentium 166. I am not sure if there is an actual benchmark that determines this rating (there must be, eh?). Intel Pentiums and Pentium IIs just happen to score a PR rating almost identical to their mhz. The same can be said for AMD K6/K6-2/K6-III. The fact that our Durons and Athlons (not sure about the PIIIs and P4s) PR rating is quite a bit higher than their mhz is due to the superior architectures in these processors that allow them to do more per clock cycle than earlier CPUs. I think they include PR rating in SANDRA for all us old [censored]s who remember the old days.

Hope this helps.