Hyperthreading in P4 Xeon (question)

[Mark Hahn]

> What is the realistic effect of "hyperthreading" in P4 Xeon?  I'm not
> versed in the latest CPU trends.  Does it mean that dual-P4Xeon will
> behave like 4-way SMP?

for some value of "behave like" ;)
that is, it will definitely NOT get twice as fast.  but it will appear
to have 4 CPUs, and can run 4 threads/procs at once (for values of 
"once" > 1 clock cycle ;)

we did a quick test on a dual-prestonia here, and saw a ~5% speedup
on a probably cache-friendly, compute-bound task.