TSC Timecounter and multi-core/SMP

[Poul-Henning Kamp]

In message <48080276.3040203 at elischer.org>, Julian Elischer writes:
>David O'Brien wrote:
>
>> 
>> The TSC on K8 is not invariant - its rate of change is affected by
>> P-state changes.
>> 
>> The TSC on Greyhound (Family 10h) is invariant.
>> [but as stated above, is not synced with other cores]
>
>You'd think that an invariant sync'd clock (fast to read) of some
>type would have been done by someone by now.. The software people
>have been asking for this for the last decade at least.

Actually one of the original design documents for SAGE stressed that
such hardware were crucially important "for any system operating
in real time", so yes, the HW people have had adequate notices.

Poul-Henning


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