Author: Robert Hyatt
Date: 19:33:47 10/26/01
Go up one level in this thread
On October 26, 2001 at 21:43:35, Tom Kerrigan wrote: >On October 26, 2001 at 21:19:11, Robert Hyatt wrote: > >>>"The floating point unit has 32 32-bit non windowed registers, which must be >>>saved on a per-context basis" >> >>Memory fails as age increases, apparently. :) > >Maybe FPUs are studied in a semester of comp org that you didn't teach. Actually FPUS really aren't touched on in a one-semester architecture course. With pipelines, cache, memory management, plus a few specific architectures, time runs out pretty quickly. > >>There is only _one_ data path _into_ the CPU. I was originally talking about >>the 64 bit chunks that can flow into the cpu from outside. And that is a >>real bottleneck on Intel boxes, still. IE you can't possible load >>instructions, int data, and fp data, fast enough if you have to use memory. >>And the classic SPEC benchmarks tend to stream data like crazy... > >This is going off on a tangent; Intel's decision to use a 64-bit FSB is almost >certainly based on price/performance goals and not the bitiness of any processor >internals. The FSB is 64-bit, the L2 bus is 256-bit, the SSE datapaths are >128-bit, the x87 FPU is 64-bit (I believe), the core is 32-bit... all design >decisions determined by any number of factors. It would have been a small amount >of work to make the P4 a 64-bit chip instead of a 32-bit chip; this wasn't done >almost certainly because the need for 64-bit is too small to justify a new >instruction set. Or they didn't want the P4 to compete directly with the Itanic >(and kick it in the nuts). AMD seems pretty happy to go the 64-bit route with >x86-64 and minimal changes to the Athlon design. > >-Tom In any case, I still believe the _driving_ force for 64 bit machines is not memory, since I still don't see any > 4gig machines lying around. But I do see a lot of people comparing FP performance to choose their next high-performance workstation. The best example here is still the Cray. With a 32 bit address bus, but a huge data path. Ditto for comparing the processors made by everybody, to the intel X86. Everybody has done 64 bit processors, but hardly any go beyond 2^32 address lines. Seems to me that it is for reasons other than address space, based on that...
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.