[TriLUG] Hyperthreading and Xeons

[Joseph Mack]

Joseph Mack wrote:
> 
> Jeremy Portzer wrote:
> >
> 
> > Does this mean that I should treat it as a four-processor computer for
> > the purposes of starting processes?
> 
> sure, but remember that the extra 2 processors are memory bandwidth limited.

even in a standard x86 2-way SMP machine, the 2nd CPU is I/O bound. The reason
the SMP Alpha machines were so good was because they had an expensive crossbar
switch which allowed simultaneous communication between pairs of devices.

SMP on the standard x86 mobos doesn't get you much in real applications running 100% CPU

Joe

-- 
Joseph Mack PhD, High Performance Computing & Scientific Visualization
LMIT, Supporting the EPA Research Triangle Park, NC 919-541-0007
Federal Contact - John B. Smith 919-541-1087 - smith.johnb at epa.gov