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SubjectRe: can TSC tick with different speeds on SMP?
Date
IIRC, in the IA64 manuals Intel, by carefully not making any guarantees 
to the contrary, reserved the right to have the TSC-equivalent register
not be synchronized either to the bus clock or the CPU clock.

This doesn't directly apply to IA32, but may give a hint as to their
future intentions.


On Monday 21 June 2004 12:02 pm, Kirill Korotaev wrote:
> Hello,
>
> I've got some stupid question to SMP gurus and would be very thankful
> for the details. I suddenly faced an SMP system where different P4
> cpus were installed (with different steppings). This resulted in
> different CPU clock speeds and different speeds of time stamp
> counters on these CPUs. I faced the problem during some timings I
> measured in the kernel.
>
> So the question is "is such system compliant with SMP
> specification?". In old kernels there was a code to syncronize TSCs
> and to detect if they were screwed up. Current kernels do not have
> such code. Is it intentional? I suppose there is some code in kernel
> which won't work find on such systems (real-time threads timing
> accounting and so on).
>
> Thanks in advance,
> Kirill
>
> -
>

--
James Cleverdon
IBM LTC (xSeries Linux Solutions)
{jamesclv(Unix, preferred), cleverdj(Notes)} at us dot ibm dot comm

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