[Xen-devel] Re: HPET/PIT timer accuracy

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"Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>

Subject:

[Xen-devel] Re: HPET/PIT timer accuracy

From:

Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>

Date:

Fri, 29 Jul 2005 19:30:33 +0100

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On 29 Jul 2005, at 18:53, Ian Pratt wrote:

Any ideas what could be going on?! This is something of a
pain for the new time code, which syncs the local TSCs to the
chipset timer....


These systems haven't got a 'spread spectrum'[*] PCI bus clock per
chance? It might be worth seeing if there's a BIOS option for it.

I did check one of our machines, and spread spectrum was definitelydisabled. In any case, I'd expect that to jitter the clock at some highfrequency, but not add/remove ticks in a way that would be discernableat 1Hz.


 -- Keir


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