Author: Steven Edwards
Date: 13:30:33 04/27/05
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On April 27, 2005 at 12:04:58, Tord Romstad wrote: >On April 27, 2005 at 11:29:07, John Sidles wrote: >>Is this the newest "ultimate" desktop chess computer? > >Absolutely not. The G5 is a rather slow processor for chess programs, and for >integer computations in general (its strong side is floating-point operations, >which are not important for chess programs). To take advantage of a 64 bit architecture, a program has to be recompiled for it. Merely running unaltered 32 binaries is not going to show that much of an improvement. For a bitboard program, having a full range of 64 instructions means a vast performance increase. This is true for PowerPC and for x86 CPUs as well. I don't own a G5, but back a couple years ago when they first appeared in Apple Stores I brought in some of my own bitboard chess software (carried on my iPod) and ran some benchmarks. I was impressed, and so Symbolic was designed from the start to be able to take advantage of a 64 bit machine -- when I have the budget for one. Someday. >My iMac G5 1.8 GHz, for instance, is clearly slower than the old Pentium IV >2.4 GHz in my office, for all the chess programs I have tried. Not even >64-bit programs like Crafty are faster on the G5. Maybe, but were the programs correctly recompiled for the 32 bit pointer/64 bit register model? For bitboard programs, the NextSq/FirstSq/CountSqs macros (and related low level functions) should be recoded appropriately. Also, the compiler should be told to use G5 instruction scheduling instead of the default universal mode. Of interest are anecdotal reports that the new optimization strategies in gcc 4.0 are giving 20%-30% speed increases in general purpose code on G4/G5 targets. This is to me the only big reason to buy Mac OSX 10.4 Tiger. >A dual 2.7 GHz G5 is of course much faster than a single 1.8 GHz, but it still >not >even remotely close to a dual opteron. There are significant differences between the iMac and PowerMac system bus implementations. That's one of the reasons the PowerMac costs a lot more. >The PowerMac G5 is an awesome machine, but if the "ultimate desktop chess >computer" is what you are looking for, you should look elsewhere. If someone is merely interested in running free downloadable binaries (nothing wrong with that), then I'd suggest an x86 machine, not a Macintosh. But for developers, it's a different story. Check out the discusstion at: http://apple.slashdot.org/
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