Author: Vincent Diepeveen
Date: 17:48:01 04/13/03
Go up one level in this thread
On April 13, 2003 at 20:41:32, Jeremiah Penery wrote: >On April 13, 2003 at 08:14:54, Vincent Diepeveen wrote: > >>On April 13, 2003 at 08:02:34, Vincent Diepeveen wrote: >> >>Hello Tom, >> >>For the endusers there is only 1 way to easily say what SMT is. That is that the >>P4 processor can split itself into 2 processors and that they get that second >>processor for free and it speeds DIEP up about 15% in nodes a second. >> >>It may be clear that this is not how i see SMT. I assume SMT is that intel has >>put 2 processors near each other which share resources. Using those resources >>probably is what takes care they cannot run both at full speed. > >Your way of seeing SMT is wrong. Everything is exactly the same as a >single-processor P4 except that the RAT (Register Allocation Table) and a couple >other things are duplicated when using SMT. Execution Resources, Caches >(including Trace Cache), Registers[1], and almost everything else are shared in >some way. > >[1] Each logical CPU can use the 8 normal x86 registers. The P4 has some 128 >integer and 128 FP physical (rename) registers, which are split up in halves >when using SMT. Each logical CPU has access to half of the physical registers. > >For a very excellent article on SMT, go to Ars-Technica. Here is a link: >http://arstechnica.com/paedia/h/hyperthreading/hyperthreading-1.html > >>In future hopefully less and less resources get shared, until only L2 cache gets >>shared where also reads can be done simultaneously, but only a write will be >>blocking other cpu from reading/writing to the L2. Then HT will give a major >>boost in speed. It is questionable whether we must call it HT then however. I >>guess intel will keep using that word for the coming 10 years though. > >That would be much more like the IBM Power4 design, which is more of a CMP thing >than an SMT thing. I bet intel will call P4-Prescott to be SMT too instead of CMP. But do you really believe it's SMT? Best regards, Vincent
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.