Author: Joshua Lee
Date: 14:47:11 07/11/02
Go up one level in this thread
On July 11, 2002 at 12:30:50, Matthew Hull wrote: >On July 11, 2002 at 00:18:36, Robert Hyatt wrote: > >>On July 10, 2002 at 12:53:11, Joshua Lee wrote: >> >>>On July 09, 2002 at 13:28:54, Robert Hyatt wrote: >>> >>>>It doesn't... For example, the C90 had a 2 nanosecond clock. The cpu >>>>could read two 64 bit words and write one 64 bit word per clock cycle, >>>>per cpu. With 16 cpus, that is 16 * 24 * 500000000 bytes per second >>>>and that can be _sustained_ forever. >>>> >>>>Compare that to any PC you want and you see why (a) the supercomputers are >>>>so expensive and (b) why the micros have absolutely no chance at catching >>>>them in terms of speed. >>>> >>>192,000,000,000 bytes per second >>>That's over 178 Gigabytes a second. Is Bandwidth refered to in this way or how >>>fast the memory can communicate with the cpu or both? In Athlon's it's has a 2.1 >>>GB/Sec bus it can execute a multiply and add on every clock cycle which gives it >>>a peak throughput of 3.2 gigaflops. >>> >> >> >>I don't see any way a 2.1 gigabyte per second memory bandwidth can translate >>into 3.2 gigaflops. A flop requires accessing two operands, doing something >>to them, and putting the result back... IE a flop == 12 bytes of memory >>traffic (cache doesn't count because big applications and arrays don't fit >>into cache). That translates into maybe 100 gigaflops as a more realistic >>number... And I don't believe any PC has a prayer of coming within a factor >>of 10 of that number in reality. > >Right! Even Apple only of only a little more than 1 gigaflop for a 500mhz G4, >which has it's own vector processor (ALTIVEC). And this chip flogs any x86 chip >as far as FLOPS is concerned. It's the classic memory bottleneck of the micro. >Bus speed versus processor speed equals wait states, or something like that. The Memory bandwidth i quoted from microway's site was how fast the memory was communicating to the cpu ,i didn't think this translated into Gigaflops but for all i knew it may be effecting it. My question then is how is a chess program using memory bandwith or how is it using the Floating point capabilities of the cpu? I thought that most chess engines are using interger strength anyway.
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