Author: Jeremiah Penery
Date: 14:01:36 07/04/03
Go up one level in this thread
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. 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.
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