only one logical CPU used in Xeon

[John Baldwin]

On Thursday 12 March 2009 10:28:15 am won.derick at yahoo.com wrote:
> 
> --- On Thu, 3/12/09, John Baldwin <jhb at freebsd.org> wrote:
> > 
> > -----Inline Attachment Follows-----
> > 
> > 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:
> > > 
> > >  > Features = 0xbfebfbff <...,HTT,...>
> > > 
> > > The "HTT" bit in the features bitmask indicates that
> > the
> > > processor supports hyperthreading.
> > 
> > No, that flag just means it supports a register where you
> > can ask for the 
> > total number of threads/cores per package.  Multi-core
> > CPUs that don't have 
> > hyperthreads have 'HTT' set, but when you read the
> > registers properly you see 
> > that they have 1 thread per core.
> > 
> 
> Does this mean that the # of logical CPUs per core is not enough to 
determine whether the machine supports hyperthreading or not? You've said 
earlier that the newer machine is not hyperthreaded, so I'm assuming that 
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 multiple 
threads in their cores, but neither of your systems have those CPUs.

-- 
John Baldwin