[geeks] New small Intel Board

[Joshua Boyd]

On Fri, Jun 06, 2008 at 04:03:17PM -0400, Alois Hammer wrote:
> On Fri, 6 Jun 2008 12:51:50 -0400 (EDT), nate at portents.com said:
> > 
> > > Hyper-threading
> > 
> > Atom does have hyperthreading (just as Nehalem will).
> 
> I'm a bit puzzled.  HyperThreading was invented because the Pentium 4
> architecture -- Willamette through Cedar Mill -- had some unused
> execution unit time resulting from the poor design, and presenting an
> extra logical CPU got a little of the lost performance back.  Why is HT
> suddenly making a return?
> 
> ...Intel hasn't suddenly added *real* threading a la SPARC T1/T2, have
> they?

Err, hyperthreading was/is real threading.  I believe the T1/T2s just
double the number of contexts per core, although there could be other
improvements that I am not aware of.

Good CPU time or not, you will still have cache faults.  However,
hopefully when thread A faults, thread Bs data will have been loaded
into the cache in the background, so why not switch hardware contexts
and chew on thread B while thread A's data is loaded into cache?