Author: Aaron Gordon
Date: 11:46:27 04/21/03
Go up one level in this thread
On April 21, 2003 at 14:36:37, Tom Kerrigan wrote: >On April 21, 2003 at 10:05:15, Aaron Gordon wrote: > >>On April 21, 2003 at 07:19:50, Tom Kerrigan wrote: >> >>>On April 21, 2003 at 05:05:08, Aaron Gordon wrote: >>> >>>>The same way a Celeron 1GHz, P3-933MHz or 900MHz Athlon is faster than a Pentium >>>>4 1.5GHz. MHz isn't everything. Pentium 4's were made with only 1 thing in mind, >>>>marketing. Make a chip with high MHz so people will think it's faster. To get >>>>those high MHz numbers they had to gimp the CPU, which is why the Pentium 4's >>>>are ridiculously slow MHz for MHz. >>>> >>>>In some applications it has the IPC (instructions per cycle) of a 486. I don't >>>>know about you, but I upgraded from a 486 a long time ago.. :) >>> >>>What part of the P4 is gimped? >>> >>>According to SPECint, >>> >>>http://www.aceshardware.com/SPECmine/index.jsp?b=0&s=2&v=2&if=0&r1f=2&r2f=0&m1f=0&m2f=0&o=0&o=1 >>> >>>AXP only has 15% more IPC than a P4. Also notice that the AXP has dramatically >>>lower IPC than MIPSs, PA-RISCs, POWERs, and Alphas. Surely you will argue that >>>AMD sacrificed IPC for clock speed for a net gain in performance. Perfectly >>>legitimate argument, and the same argument one could make for the P4. >> >>Well, when you start needing P4's running nearly 6GHz to equal my AthlonXP >>2.5GHz in some things, you have to admit they screwed that chip pretty bad. >>Lots of stuff like rendering, simulations, etc, all run slow. > >Not really. Processors have their strengths and weaknesses. I'm sure you could >find some pathological code that runs much slower on the Athlon than the P4. If you find anything, let me know. So far I know of nothing. I however know of *MANY* things that run pitiful on a p4. >>Also here is something I found a while back, put it on my page for later >>reference. http://speedycpu.dyndns.org/old/p4sucks.html > >This guy is a moron. He goes on and on about the P4's L1 dcache as if the >engineers at Intel all ride the short bus to school and somehow forgot to put >some more cache on the chip. Any idiot knows that the P4 has such a small dcache >because Intel wanted a cache with a 2 cycle latency instead of the 3 cycle >latency of the Athlon and P6. If Intel's measurements and simulations indicated >that a 3 cycle cache would be better, don't you think they would have put one >in? I mean, it's not like a 3 cycle cache is harder to design than a 2 cycle >cache (it's easier) and Intel's done it before, obviously. And if all Intel was >after was high clock speeds, putting low latency caches on their chips isn't the >way to go about it. > >If you look at all this guy's points with the mindset of "there must be a reason >why they did this" instead of "man are they idiots," it's pretty easy to take >apart all of his lame arguments. > >>>BTW, while I definitely share your enthusiasm for Opteron, I wouldn't get >>>people's hopes up with talk of blazing speed. Chess programs run mainly in >>>cache, so the on-die memory controller won't help much. Chess programs don't >>>require a ton of inter-processor bandwidth, so HT won't help much. Chess >>>programs may benefit significantly from x86-64 in the future but high-quality >>>x86-64 compilers won't be here for a while. What's left? Some improvements to >>>the core, which may or may not be offset by the higher branch mispredict >>>penalties, and I doubt they'd make up for the 15+% difference in clock speed >>>between the Opteron and the AXP. I expect AMD to ramp up Opteron (and A64) clock >>>speeds quickly, so they will be quite good for computer chess, but this week >>>won't offer anything mind-bending to computer chess enthusiasts. >>> >>>-Tom >> >>Chess engines that use bitboards should get a nice boost. The results I saw from >>a Clawhammer running a modified Crafty in linux absolutely annihilated the >>AthlonXP MHz for MHz. I'm not talking by 40-50% either.. > >How does gcc compare to VC or Intel C for Crafty? >-Tom Intel C is much faster than gcc and slightly faster than VC in my tests. I find Intel C 5.0.1 faster for Athlons but what AMD used for the testing was the latest, 7.0.
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