Author: Matt Taylor
Date: 14:23:34 12/03/02
Go up one level in this thread
On December 02, 2002 at 10:20:42, Robert Hyatt wrote: >On December 02, 2002 at 02:52:17, Gian-Carlo Pascutto wrote: > >>On December 01, 2002 at 21:04:54, Arshad F. Syed wrote: >> >>>I am not much of an expert on this, since I am just starting to get into >>>assembly programming. But I was curious about the dword used here, which implies >>>to me you are doing 32-bit stuff. Wouldn't it make life simpler to just get an >>>Itanium processor and switch to 64-bit code, which would cut down the cycles >>>used. >> >>They're $$$ like $$$ expensive $$$ ! >> >>But yes, having a 64-bit CPU makes all this kind of stuff easier >>and faster. Hopefully we'll get fast and affordable ones soon. >> >>-- >>GCP > > >They are definitely not cheap at the moment. An Itanium2 at 900 mhz goes >for about $2,800 bucks on Pricewatch. That will produce NPS values of > >1.5M for Crafty, for reference (don't think a 900mhz itanium will get blown >off by a 3ghz PIV for example) and possibly higher with some asm tweaking >as has been done by Eugene for the X86 version... It is possible to do a lot of atomic 64-bit computation on our "32-bit" CPUs. In SSE 2, you can, I believe, perform every basic ALU operation on a 64-bit quantity using the MMX unit. You can also do 2 at a time using the SSE registers (128-bits wide). On my AthlonMP 1600, not so graced with SSE 2 instructions, I can still emulate any basic ALU op (add, or, sub, and, xor, cmp, not, test, inc, dec) at roughly half of 32-bit integer performance without SSE 2. This gives me about 1 IPC throughput in 64-bit arithmetic utilizing solely the integer unit. Someone tricky could also use the FPU in parallel for the same job and get performance gains of probably 30-40%. Also, someone even more clever could probably find a way to use the SSE unit for about 4 times the performance (minus the cost of emulation).
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