Author: Tom Kerrigan
Date: 01:12:20 12/07/99
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Intel says a lot about how many registers the "Itanium" has, but they only make a small fraction of them available to the user. The design is supposed to be really great because when it gets to a branch, it can start working on both paths while the branch condition is still being evaluated. You can imagine this sucks a lot of registers... (I'm just repeating some secondhand information. I could be totally wrong...) -Tom On December 06, 1999 at 08:39:37, Vincent Diepeveen wrote: >On December 05, 1999 at 20:31:41, Jeremiah Penery wrote: > >>On December 05, 1999 at 19:41:00, Vincent Diepeveen wrote: >> >>>On December 05, 1999 at 12:59:09, Werner Schuele wrote: >>> >>>>Can anybody post chess-benchmarks for PIII 600E or PIII 650/700?. >>>>I wonder if Athlon or PIII is the better chess-processor. >>>>Thanks >>>>Werner >>> >>>Athlon is a gift from heaven. >>> >>>It's 15.5% faster than a PIII for DIEP, >>>and i can only pray that a dual and quad motherboard for it >>>gets out real soon and competes with intel in such a way that >>>quad motherboards get cheaper, yes even octo motherboards... >>> >>>Note that celeron is also quicker than PIII, about 7.2% for DIEP, >>>but parallel of course it doesn't get near that, it's about >>>as fast as a PIII for the parallel version of DIEP, so when >>>talking about parallellism, please let the dual boards already come >>>from AMD... ...especially now that a 1 Ghz AMD is available (kryoteched >>>cooled and overclocked SuperG stable at 1 Ghz, see www.kryotech.com) >> >>Have you tried Diep on the Coppermine PIIIs, as opposed to the Katmai ones? I >>saw benchmarks (from PC Magazine or something...) where the Coppermine was up to >>40% faster in raw integer/FP calculating speed than a Katmai PIII at the same >>speed (MHz). This is due to a number of factors, which I won't go into now... >>With the Coppermine, the PIII is just as fast as the Athlon. > >Wherever i look, i can't find a single dealer which has a coppermine >available. This is like saying: wait for the k8 to come out. Let's >get real and clearly distinguish between processors that we can buy >and processors that get out one day. > >Note that intel promised till few months before it was available >that Katmai would be 15-25% faster than a PII, yet for integer instructions >it appeared to be 100% the same as the PII. Let's relax and wait for the >coppermine to get introduced and then draw some conclusions. > >For now my favourite 2 processors are the K7 and the 21264. > >Note that from AMD i wasn't given any details how their branch prediction >works, in contradiction to dec-alpha for the alpha 21264 which seems to >have a superb form of branch prediction. Took AMD 1 month to reply to >an email of mine. It's a 2k big table that's all i know. > >The penalty for a misprediction is *at least* 10 clocks at AMD, >so a clock more than what PIII does give. So being 15.5% faster than >a PIII for DIEP is theoretical kind of weird. > >Except for the 21264 which does 4 instructions a clock, they all do 3 >instructions a clock. > >The interesting details list to know from any CPU for chessprograms: > - #instructions a clock > - number of integer registers (merced gonna have 128!!!!!) > - L1 code/data cache sizes > - L2 speed and size > - new form of branch prediction (hopefully copied from dec alpha?)? > - #entries for Branch prediction table (512 only for the PRO/PII/PIII). > - smallest delay for a branch misprediction > - 64 bits? > >Expected speedups for possible changes assuming the processor is a PIII >and then gets next projected on DIEP on a new CPU with just one change: > >If a CPU does 4 instructions a clock instead of 3, then that obviously >should speed up roughly 30%. > >More registers kick butt bigtime (unlikely that >intel changes this till the merced comes out as this would require new >compiler and incompatibility with current software), but i have no >idea how much it would speedup my program. > >making L1 cache from 32 kb to 128 kb gives nearly 10% speedwin. >Speeding up the L2 cache to processor speed (doubling in speed), about 7% >speedwin (if both L1 cache gets bigger and L2 gets faster then i guess total >speedup is less way less than 17%). > >new form of branch prediction (let's take the alpha branch prediction) >i can only guess here bigtime: 25% speedup? > >increasing BTB (branch target buffer on intel processors) or branch >prediction table from 512 to 2048 ==> 10% speedup. > >If hardly delay for branch mispredictions i'd >expect my program to get 2 times faster... > >Getting a 64 bits processor is interesting to know for Bob, >not for DIEP though. > >What i don't have are these details for the SUNSPARC processor. >For crafty this processor sucks bigtime, even though it's a 64 bits >processor. >DIEP isn't fast either on these processors, though it's not that slow. >a 300Mhz sun performs like a 233Mhz PII for DIEP nowadays or a bit >faster than a pro200Mhz. At the sun i used gcc 2.95.1, and considering >this compiler is at intel processors around 8% slower than the visual >compiler, that would make the sun look like a bit better: >==> 233 x 1.08 = 252Mhz PII which means that a PII at the same Mhz is >less than 20% faster. > >Vincent
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