Author: Robert Hyatt
Date: 20:34:54 10/04/99
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On October 04, 1999 at 20:03:52, Will Singleton wrote: > >I'm looking at the specs for the 500mhz G4 (available someday), and I'm >wondering about a couple things. > >The AltiVec, or "Velocity Engine", is apparently a vector processing unit for >which special code must be written to obtain speedups. I wonder if this means >that the compiler must support those instructions, or can you take advantage of >vector processing just by rewriting existing code? > >Is the vector-processor used mainly in FP operations, or can it be helpful for >integer-based code? > >The specs say that it has data stream prefetching ops supporting 4 simultaneous >32-bit data streams, as well as a new fpu supporting single-cycle, >double-precision calcs. Are both of these associated with the vector processing >unit? > >In short, can a chess program take advantage of vector processing without a >massive rewrite? > >Will Hard to say. Vector machines generally have higher bandwidth between the CPU and memory, for vector reads/writes (only). But this means that if you are clever you can suck in more data, faster. They also provide some wild capabilities that take a while to get used to... and yes, to make the program really fly on such a machine, a _lot_ of rewriting is in order... but first you have to study the architecture a good while and learn to 'think vectors'... We continually optimized/vectorized Cray Blitz for almost 15 years... and there was still room for more vectorization...
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