Author: Vincent Diepeveen
Date: 04:05:26 03/25/02
Go up one level in this thread
On March 24, 2002 at 21:42:32, Robert Hyatt wrote: >On March 24, 2002 at 21:10:57, Eugene Nalimov wrote: > >> >>We are talking about *absolute* performance, not about "nodes per MHz", right? >>Right now I can buy 2.2GHz x86 system, but I believe that fastest Alpha is 1GHz. >> >>I just run Crafty's "bench" on my 1.13Hz notebook and got 620knps, and I think >>that fastest x86 system will be faster than fastest Alpha. >> >>Eugene > >First, several mis-matches. > >1. I used gcc to compile Crafty, which Tim used to compile on the alpha. >So there is no compiler differences that are very significant... >2. I believe that Vincent has been saying that 64 bit processors simply >don't help. This is incorrect. They help significantly. There is no >technical reason why a 64 bit processor can't be clocked just as fast as >a 32 bit processor. The marketing force is simply not driving the development In a year or 10 you may be right, for now not a single 64 bits processor is clocked *near* 32 bits processors. You are still busy with stupid old 600Mhz 21264 processors. I tested myself on the mothers. They suck ass for computerchess, the only interesting is absolute performance, not how fast they are for 600Mhz, because in CPU design the L1 and L2 cache are very important. If they didn't manage to clock those at 1.6Ghz, then that's their problem, not mine. For FPU, that's another story, that's not computer chess. >that way _yet_. But if someone wants to make a fast 64 bit chip, and believes >that they can market it to make a profit, then it will happen. Oh they will come, no doubts here that it will happen. Look at the McKinley design. Of course i can't pay a mckinley, but you could put perhaps 16 in parallel on a supercomputer. Will be perhaps even cheaper than the 10 million dollars for a 16 processor 21264 system. Of course clocked at 1Ghz each. >3. If you use gcc, your 1.13ghz notebook will be well off that pace, and >that will put it back into the light of a relatively equal comparison since >we would all be using the same compiler. This is dead wrong of course. you use the compiler that's fastest for the processor. If you look well at the specbench.org site you'll see that they also quote which compiler is used. Compaq C V6.4-214-46B59 Program Analysis Tools V2.0 Spike V5.2 DTK (1.461 46B5P) Compaq C++ V6.3-010-46B2F So they first analyzed the program and only after that recompiled it in order to get faster. It is very EASY to see that this is the fastest compiler for the Alpha. Amazingly for the XP2000 used was the intel compiler. Even though i don't trust this compiler at all for my software. >I was personally far more interested in the nps per megahertz since that seemed >to be the point vincent was attacking the alpha on, and the numbers don't >support his argument at all... No that's not interesting Bob. You know it and i know that they can easily clock L1/L2 cache at 1Ghz nowadays, but try to clock it at 2Ghz!! Of course a machine at 2.2Ghz or 1.67Ghz is going to have more problems clocking the caches higher. The only INTERESTING thing is how fast a processor + compiler performs for a program. If you build a 1Ghz processor, then it gotta beat a 2Ghz K7 simply. If it doesn't, THEN YOU ARE SLOWER. >>>I don't know the specifics about the dual, but it was only 1.5X faster. We >>>later improved this a lot as the "lock" facility we used to start with was >>>very slow on the alpha architecture. >>> >>> >>> >>> >>>> >>>>Relative to the 1.67Ghz from the K7 the alpha achieves like >>>>a 102/122 x 1.667Ghz = 1.394Ghz K7 >>> >>> >>>Show me that 600mhz K7 that can do .8M nodes per second with crafty... Show me the alpha that can beat a 1.67Ghz XP, YOU WILL NOT FIND IT. In fact it is 30% slower even for CRAFTY which is supposed to profit from 64 bits. So a 32 bits processor doing 3 instructions a clock is kicking the HELL out of a 64 bits processor doing 4 instructions a clock, the 32 bits processor being clocked higher only 60%. VERY HARD DATA!! Alpha sucks simply bigtime for the kind of integer operations a chess program is using, that's a *logical* conclusion to draw. And yes, the alpha compiler is using many instructions to remove branches, the X86 guys didn't invent those themselves... >>>Then I'll be a believer, not now... >>> >>> >>>> >>>>In theory the 4 instructions a clock for alpha versus >>>>3 instructions a clock for K7 give 33% speedup: >>>> >>>>1.000 Ghz + 33% = 1.333Ghz >>>> >>>>It achieves however 1.394Ghz >>>> >>>>In short i am missing the speedup for being 64 bits at all! >>> >>> >>>Because you are looking at the wrong data.. :) >>> >>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>>> >>>>> >>>>>>> >>>>>>>>-Tom
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