Hyperthreading hurts 5.3?

Chuck Swiger cswiger at mac.com
Tue Jan 11 18:31:28 PST 2005

Timothy J. Luoma wrote:
> summary: should I disable hypertheading in the  BIOS when running 5.3?

It would certainly be worth trying this and seeing whether running as a purely 
single-proc system performs better for you.

It's not exactly as if HyperThreading evolved out of a sensible plan like 
"let's design a multi-core CPU intended for parallel execution, or something 
like a m56k DSP with VLIW", the situation is more like "Intel created the P4 
such a monsterously long pipeline that breaks x86 instructions into tiny u-ops 
which require a lot of functional units to be available, only the CPU still 
can't schedule things to use all of the available units much of the time, 
anyway, so hey, maybe we could run another processing thread on 'em and hope 
the additional work it can do outweighs the additional CPU resource contention 
and the additional overhead of doing SMP..."

[ I have a non-HT P4 (a 2.4MHz at 400FSB Northwood) around, but I doubt I'd turn 
HT on with it even if it could.  I'd rather use an AMD-64, or a G5, or even a 
recent P3 (Tualatin/Pentium-M) than another hyperthermal P4 spaceheater. ]

Bah, I'm rambling, time to stop... :-)


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