Messages in this thread | | | Date | Wed, 29 Mar 2000 03:21:14 -0800 | From | "H. Peter Anvin" <> | Subject | Re: Timestamp counters on SMP |
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Alan Cox wrote: > > > there are notebooks which change the CPU speed and voltage (and the TSC > > speed as well), depending on the load. This is a much bigger problem. > > Current x86 notebooks dont change the TSC speed. They change the clock duty > cycle not the clock rate. >
Correct. Transmeta Longrun and Intel Speedstep do change the clock frequency, though; however, at least Transmeta will still present a constant-frequency TSC to the RDTSC instruction. Don't know about Intel.
(Now, some broken Cyrix chips would lose or not increment the TSC when throttled.)
-hpa
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