Author: Robert Hyatt
Date: 19:28:55 03/03/00
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On March 03, 2000 at 22:19:51, Jeremiah Penery wrote: >On March 03, 2000 at 20:05:57, Tom Kerrigan wrote: > >>On March 03, 2000 at 17:08:58, Robert Hyatt wrote: >> >>>Problem is the compilers don't know what is going on. IE how many "hidden" >>>registers does the architecture have for renaming? Intel (nor anyone else) >>>will make this a 'constant'. >> >>But my point is, why have register renaming at all. I can list a dozen good >>processors that don't do it. I would like to know the exact percentage speedup >>it gives you. >> >>>And how does the P5 do more per cycle than a P6 when the p6 can do three >>>ops/cycle, while the P5 drags along at a max of 2, and it requires a very >>>good compiler to do two at a time??? >> >>TSCP (1.42) on an original Pentium/200 searches 136 NPS/MHz. >> >>On a Pentium II/300, it searches 119 NPS/MHz. >> >>So the Pentium appears to be 15% faster, despite its lack of out-of-order >>execution, branch predition, speculative execution, register renaming, >>reservation stations, blah blah blah. >> >>I assume this is because the P5 has shorter pipes and doesn't have to flush them >>all the time due to speculative execution gone wrong. >> >>(BTW, the K5 has almost everything beat. It searches 173 NPS/MHz, and it doesn't >>do anything particularly fancy either.) > >Maybe your original statement should have been more like: "_For TSCP_, the >original Pentium does more work per clock-cycle than the PII." Because this >will likely not be the case for other programs. I know a lot of programs favor >the AMD chips over the Intel ones. There are other programs that highly favor >the Intel chips. Crafty, for instance, does a bunch more work/cycle on the >Intel P6 chips than it does on any other chips (not including Alpha and such). I wasn't thinking carefully earlier, but should have suggested that maybe TSCP is much smaller and more 'cache-friendly' than a larger program like crafty. The AMD processors had historically had a good cache/cpu interface, which would favor such a program more than one needing good memory bandwidth.
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