Re: 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.