Author: Vincent Diepeveen
Date: 15:21:08 07/04/03
Go up one level in this thread
On July 04, 2003 at 17:01:36, Jeremiah Penery wrote: >On July 04, 2003 at 14:37:37, Vincent Diepeveen wrote: > >>On July 03, 2003 at 16:48:07, Tom Kerrigan wrote: >> >>>On July 03, 2003 at 16:23:10, Russell Reagan wrote: >>> >>>>On July 03, 2003 at 15:02:55, Joachim Rang wrote: >>>> >>>>>The main reason is, that Athlon and P3 have 9 instructions per cycle and P4 has >>>>>only 6. >>>> >>>>Also the length of the pipeline on the P3 is 10, which means that a mispredicted >>>>branch costs 10 cycles. On the P4 the length of the pipeline is 20, which means >>>>it costs 20 cycles for a mispredicted branch. I may be wrong about the actual >>>>numbers (10 and 20, but I think they are close). I'm not sure what the length is >>>>on the Athlon. Anyone know? >>> >>>Pentium 3: 12 cycles >> >>9+ cycles. Usually it's more like 15 though when you measure. >> >>>Pentium 4: 20 cycles >> >>20+ usually it's more like 30+ though. >> >>>Athlon: 10 cycles >> >>there is no official data on this and i won't sign a NDA ever of either intel or >>AMD. AMD answerred my public question a few years ago: >> >>"Mr Diepeveen, it is more than the P3, but the exact amount is secret" > >You're spewing gibberish again. The pipelines of all of these processers are >very well documented. I don't know what numbers you're trying to give. Maybe >you're confusing pipeline length with branch misprediction penalty. Of course the pipe line length is not so interesting, but the resulting branch misprediction penalty out of it is! >The pipeline of a P4 is exactly 20 stages long, no more and no less. It's well >documented by Intel and elsewhere. >Athlon's pipeline length is 10 for integer and 15 for floating-point. Directly >from AMD here: >http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/22054.pdf >and also from MANY other sources. > >As for the P3, every source I could find gave a pipeline length of 10 stages. >>This is my only big criticism to AMD. If they release more specs about their >>processors then everyone can tune better for it. I understand very well why > >http://www.amd.com/products/cpg/athlon/techdocs/pdf/22007.pdf > >>most >>assembly optimized software runs so well on the intel hardware in this respect. >>What runs fast at the P4 usually is described publicly by intel. > >You can find way more information about the Athlon architecture than you can >about the P4. >The rest of what you say is completely irrelevant to the discussion. No it isn't the original poster asked why the P4/Athlon is so much faster for computerchess than the P4. As usual your short term memory i bet. Seems only slightly longer now than Bob's.
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