You could check the power policy via
CallNtPowerInformation(...ProcessorPowerPolicyCurrent...) and then inspect
the `DynamicThrottle' member. Assuming no ill-behaved drivers are going
behind the OS's back with respect to the processor throttle MSRs, this
should tell you whether the OS has enabled throttling or not.
CallNtPowerInformation(...ProcessorInformation...) can be used to retrieve
the current effective processor speed if throttling is engaged.
Ken Johnson (Skywing)
Windows SDK MVP