Re: only one logical CPU used in Xeon

On Thursday 12 March 2009 10:28:15 am [e-mail] wrote:
>=20
> --- On Thu, 3/12/09, John Baldwin <[e-mail]> wrote:
> >=20
> > -----Inline Attachment Follows-----
> >=20
> > On Wednesday 11 March 2009 11:01:51
> > am Oliver Fromme wrote:
> > > Here's how you can see the details in the demsg
> > output:
> > > The older machine:
> > >=20
> > >=A0 > Features =3D 0xbfebfbff <...,HTT,...>
> > >=20
> > > The "HTT" bit in the features bitmask indicates that
> > the
> > > processor supports hyperthreading.
> >=20
> > No, that flag just means it supports a register where you
> > can ask for the=20
> > total number of threads/cores per package.=A0 Multi-core
> > CPUs that don't have=20
> > hyperthreads have 'HTT' set, but when you read the
> > registers properly you see=20
> > that they have 1 thread per core.
> >=20
>=20
> Does this mean that the # of logical CPUs per core is not enough to=20
determine whether the machine supports hyperthreading or not? You've said=20
earlier that the newer machine is not hyperthreaded, so I'm assuming that=20
there is another part in the dmesg output that says so. more guidance pls.

Your new machine might be hyperthreaded.  I'm not really sure as it's a P4
descendant and I'm not sure if Intel released some dual-core P4 Xeon that
had 2 threads per core.  The current Core processors do not implement multi=
ple=20
threads in their cores, but neither of your systems have those CPUs.

=2D-=20
John Baldwin
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