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by tptacek 5844 days ago
Presumably the high frequency counter is driven off the cycle counter, and not the Intel High Precision HPET Timers.
1 comments

http://en.wikipedia.org/wiki/Time_Stamp_Counter

"The issue has two components: rate of tick and whether all cores (processors) have identical values in their time-keeping registers. There is no promise that the timestamp counters of multiple CPUs on a single motherboard will be synchronized. In such cases, programmers can only get reliable results by locking their code to a single CPU."

The entry also mentions that hibernation can affect the counters. I wonder if power savings implementations that speed up or slow the CPU could also have an effect.

Yes. The TSC, which counts cycles, is what WinAPI reads with GetTickCount(), and is not the same thing as the HPET timers.