Messages in this thread | | | Subject | Re: do_gettimeofday vs. rdtsc in the scheduler | From | Alan Cox <> | Date | 19 Sep 2002 14:27:19 +0100 |
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On Thu, 2002-09-19 at 12:20, Mikael Pettersson wrote: > > The local APIC timer is specified in the Intel Manual volume 3 for example. > > It's an optional feature (CPUID), but pretty much everyone has it. > > Except that like everything else related to the local APIC, you're at > the mercy of the competence (or lack thereof) of the BIOS implementors. > - There are plenty of laptops whose CPUs have local APICs but whose > BIOSen go berserk if you enable it. There are also plenty of laptops
Frequently because we don't disable it again before any APM calls I suspect. When a CPU goes into sleep mode you must disable PMC and local apic timer interrupts.
> that don't have one, since Intel removed it from many Mobile P6 CPUs. > - There are even some desktop boards with BIOS problems, including Intel's > AL440LX on which Linux must stay away from the local APIC timer. > > To assume the local APIC works on 686-class UP boxes is not realistic, alas.
Yep
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