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SubjectRe: Wrong number of cpus detected/reported
Steven Cole writes:
> On Tue, 2003-06-10 at 15:35, Alan Cox wrote:
> > > wp : yes
> > > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
> > > bogomips : 2798.38
> > >
> > > See that ht flag near the end?
> >
> > The ht flag means the ht facilities (mtrr etc) are present, doesnt mean
> > HT necessarily is
>
> Is there a reliable method, apart from knowing 'a priori' the mapping
> from CPU models and stepping to hyperthreading capability?

Yes. Execute cpuid with eax=1 on each CPU. ebx describes among other things
the number of threads and which thread you're on. If you ever find yourself
on a non-zero thread, you have HT.
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