TSC Timecounter and multi-core/SMP

[David O'Brien]

On Tue, Apr 15, 2008 at 09:46:02AM +0100, David Malone wrote:
> On Mon, Apr 14, 2008 at 09:51:42PM -1000, Jeff Roberson wrote:
> > I think we should confirm whether this is the case with earlier opterson. 
> > I have seen two processors on the same die out of sync.
> 
> This can definitely happen according to this note from AMD, which
> someone posted a link to earlier in the thread:
> 
> 	http://lkml.org/lkml/2005/11/4/173
> 
> it can happen when you hlt one core, but don't hlt the other on
> some processors.

Actually that is something slightly different.  Even without HLT, RDTSC
on the two cores of a dual-core processor can be out of sync.  HLT can
affect the delta between the two cores.

-- 
-- David  (obrien at FreeBSD.org)