Author: Robert Hyatt
Date: 20:44:42 06/29/03
Go up one level in this thread
On June 29, 2003 at 18:08:31, Vincent Diepeveen wrote: >On June 29, 2003 at 11:27:56, Sune Fischer wrote: > >>On June 29, 2003 at 11:16:51, Jay Urbanski wrote: >> >>>On June 29, 2003 at 10:45:25, Sune Fischer wrote: >>> >>>>Right, but why is this interesting? >>>>Honestly, to compile Crafty with a 32-bit compiler for a 64 bit chip smells like >>>>incompetence to me. >>>> >>>>Finally the 32-bit hell is over, for good!! :) >>> >>>>-S. >>> >>>It's interesting because the vast majority of chess engines are 32-bit binaries >>>without any source code provided. Granted if you're running Crafty you'd be >>>silly to compile it as 32-bit; but most other engines don't provide you that >>>option. >>> >>>It will be several years before we see commercial 64-bit engines for Opteron. >>>We may never see them for Itanium. >> >>Depends on what you mean by 64-bit, I don't expect the non-bitboarders to >>switch, but I'd certainly expect them to make use of it other ways, like simply >>recompiling to 64-bit and coding for the extra registers. > >this is nonsense of course. First of all intel will be releasing x86-64 cpu's >themselves. So what runs at opteron, will run in future at intel 64 bits cpu's >too (don't confuse it with the itanium line which IMHO has failed for the low >end market unless they can make them 10 times cheaper than they are now and less >buggy and clock them 2 times higher). > >apart from some trivial advantages like you can do some pawnboards in 64 bits >and 64 bits adressing, which will give some speedup and zobrist hashing that >goes a lot easier, there is other advantages. > >Take the huge BTB at the opteron. > >BTB you ask? > >yes checkout the docs. it stands for branch target buffer. It's like 8 times >that of the K7. > Size of the BTB is not _nearly_ so important as how it is implemented. Intel has a really cute approach in the PIV and it works exceptionally well. I think the idea came from a researcher somewhere in Texas (Maybe Rice but I am not certain). I'd take the new BTB design at 1/4 the size compared to traditional BTB design, without thinking about it very long... >L2 cache is 1MB. > >Though this would normally be not that relevant, it is relevant now, because >the cpu's get so much faster now that L1 cache can't do everything for you >anymore. > >Therefore the improved latency is also great. It's like 3 times faster that >latency compared to what a dual K7-MP or dual P4-Xeon. That's one I will wait to actually measure. I don't personally believe 40ns is doable, where current machines are hitting 120ns unless using registered DRAM. > >Then there is a lot of small improvements at the chip which are very important. > >But you miss one of the biggest improvements. For some reason most forget to >mention it. For years we had to do with just 8 stupid registers which get >swapped away and so on. Now we get 16 registers. > >That's a *major* improvement. > >Of course 128 GPR registers is better, but opteron will always be higher clocked >than any cpu having 128 general registers. I have no idea why you would make that statement. number of registers is _not_ related to clock speed in any real way. > >I don't want to get into the itanium versus itanic discussions (whether the >predication of the itanium is good or not) because coming tuesday i get a big >presentation of the altix3000 system which is just installed at SARA. > >I prefer showing up with 500Mhz processors though at world champs 2003 unless i >have a very hard proof that Itanium is faster for me than that (500 mips versus >64 itaniums). > >So far i didn't see any itanium system capable of more than 64 cpu's in 1 >partition or node (SGI nowadays calls a partition a 'node'. And a node is called >a calculation module or something; trivially that is because 99% of all >scientists do not know the difference between nodes at a cc-NUMA machine versus >nodes at clusters). > >That 16 registers *will* speed me up *bigtime* at opteron. I would be amazed if >it doesn't speedup others a lot. > >>This would not take years, it will happen as soon as a significant portion of >>their customers own them. >> >>You know, if there ever was a programmer who cared about the speed of his code, >>then that would be a chess programmer. :) >> >>-S.
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