Messages in this thread | | | Date | Sat, 23 Jul 2011 23:15:02 -0400 | From | Andy Lutomirski <> | Subject | Re: [PATCH v4 3/7] acpi-cpufreq: Add support for disabling dynamic overclocking |
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On 07/18/2011 12:37 PM, Matthew Garrett wrote: > One feature present in powernow-k8 that isn't present in acpi-cpufreq is > support for enabling or disabling AMD's core performance boost technology. > This patch adds that support to acpi-cpufreq, but also extends it to allow > Intel's dynamic acceleration to be disabled via the same interface. The > sysfs entry retains the cpb name for compatibility purposes. > > Signed-off-by: Matthew Garrett<mjg@redhat.com> > --- > drivers/cpufreq/acpi-cpufreq.c | 191 ++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 191 insertions(+), 0 deletions(-) >
> + if (enable) > + reg->q&= ~MSR_IA32_MISC_ENABLE_TURBO_DISABLE; > + else > + reg->q |= MSR_IA32_MISC_ENABLE_TURBO_DISABLE; > + }
I was curious and looked it up. Intel SDM volume 3, 14.3.2.1 says:
Opportunistic processor performance operation can be disabled by setting bit 38 of IA32_MISC_ENABLE. This mechanism is intended for BIOS only. If IA32_MISC_ENABLE[38] is set, CPUID.06H:EAX[1] will return 0.
and the next section says:
System software can temporarily disengage opportunistic processor performance operation by setting bit 32 of the IA32_PERF_CTL MSR (0199H), using a read- modify-write sequence on the MSR.
Would that be a better way to control boost mode on Intel chips?
--Andy
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