Author: Jeremiah Penery
Date: 18:57:11 12/10/02
Go up one level in this thread
On December 10, 2002 at 21:19:18, Matt Taylor wrote: >On December 10, 2002 at 21:13:28, Robert Hyatt wrote: > >>As far as sharing pipes, that can happen. But if one thread is burning one >>pipe up doing useless work, that is lost cycles that the other thread can't >>get to. Which is _the_ point for the "pause" instruction... > >The integer pipe feeds into 5 integer execution units which can be accessed >concurrently each cycle. However, a spin-wait loop will only be able to use 1 >unit because of register dependenies. Yes, and if you can produce ANY real-world code that will actually fill up even the 4 remaining pipes for the majority of the cycles, I'd be extremely surprised. That's why Intel has done HyperThreading in the first place - because a majority of the 'pipes' in any modern processor are going unused in any given cycle. HT is a way to make better use of those resources.
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