Hyperthreading Issues (on Athlon64?)

JoaoBR joao at matik.com.br
Tue Oct 10 16:15:24 PDT 2006

On Tuesday 10 October 2006 16:43, John Baldwin wrote:
> On Tuesday 10 October 2006 14:55, JoaoBR wrote:
> > On Tuesday 10 October 2006 15:11, Brooks Davis wrote:
> > > > My dmesg does not have the line about "Hyperthreading: 2 logical
> > > > CPUs", though.  But I had been pretty sure the Athlon64 chips didn't
> > > > have any hyperthreading support.  Why is the HTT there?
> >
> > HTT is NOT hyperthreading, HT is and HT does not exist on AMD64
> Err, no.  The HTT there stands for HyperThreading Technology.

you say it right: "stands for" in this case

But I think it "is" the other way round, in terms of abreviation:

HTT = Hyper Transport Technology
HT = Hyper Threading (Technology)


If believe Intel came up with HyperThreading after AMD brought up the term HTT 
and so there was no way to call it HTT but "HT Technology" but this story may 
be wrong.

Unluckily (my opinion) in freebsd's i386 kernel (read NOTES) HT technology is 
called HTT CPU. 

Even if this is certainly ok for whom knows it,  then an AMD X2 is definitly 
not a hyperthreaded processor but has 2 cores as well as Intel's newer Core 
Duo, so HTT for an AMD X2 would be wrong (my opinion again)

on AMD DualCore you see

  Cores per package: 2 <<<<<<<
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1

on P4 HT you see

  Logical CPUs per core: 2 <<<<<<<
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1

what then at the end is correct but it does not correct the logic error :

HT or HTT is the question but at the end AMD is not HTT, whatever HT or HTT 
then is or stands for



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