Messages in this thread |  | | Date | Mon, 1 Oct 2001 09:28:50 +0000 | From | Pavel Machek <> | Subject | Re: CPU frequency shifting "problems" |
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Hi!
> > > For example, the Intel "SpeedStep" CPU's are completely broken under > > > Linux, and real-time will advance at different speeds in DC > > and AC modes, > > > because Intel actually changes the frequency of the TSC > > _and_ they don't > > > document how to figure out that it changed. > > > > The change is APM or ACPI initiated. Intel won't tell anyone anything > > useful but Microsoft have published some of the required > > intel confidential > > information which helps a bit > > APM is a lost cause, but the correct solution for ACPI systems is to use the > PM timer. This totally obviates the need to really care about the CPU's > effective frequency at all. Even if you knew all the details of SpeedStep > (and I've seen the same MS doc you have Alan and was surprised at its > detail) you'd still be hosed if the CPU throttles...you'd be hosed in a > *good* way because at least any delays would be longer (not shorter) than > expected but your times would be off nonetheless.
And if it is thermal-throttledduring bogomips calibration...? [Well possible, acpi is not active that early]
-- Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt, details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.
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