hyper threading.

[RW]

On Saturday 26 March 2005 22:45, Anthony Atkielski wrote:
> em1897 at aol.com writes:
> > Yes, the theory is very nice; you've done a nice
> > job reading Intel's marketing garb.
>
> I haven't read their marketing materials.  I'm simply going by the
> technical descriptions I've read of the architecture.
>
> > However if you don't have a specific hyperthreading-aware scheduler
> > and particularly well-written, threaded applications, you'll lose more
> > than you'll gain.
>
> If that were true, then it would be equally true of systems with actual
> multiple physical processors.  In practice, multiple processors provide
> an obvious performance gain, and hyperthreading does, too, although it's
> much more modest than the gain obtained from physically independent
> processors.

The situation is very different.

Multiple processors can run multiple processes at the same time. A HT 
processor can only run two threads from the same process. And most software 
isn't multithreaded.