How to measure elapsed time under Windows?
gagsl-py2 at yahoo.com.ar
Wed Feb 24 18:32:59 CET 2010
En Sat, 13 Feb 2010 17:29:45 -0300, Tim Roberts <timr at probo.com> escribió:
> "Gabriel Genellina" <gagsl-py2 at yahoo.com.ar> wrote:
>> The original problem was with the RDTSC instruction on multicore CPUs;
>> different cores may yield different results because they're not
>> synchronized at all times.
> Not true. The synchronization issue has two causes: initial
> synchronization at boot time, and power management making microscopic
> adjustments to the clock rate. In Windows NT 4, Microsoft took extra
> to adjust the cycle counters on multiprocessor computers during boot so
> that the processors started out very close together. Once set, they
> naturally remained in lock step, until aggressive power management
> more prevalent. In XP, they stopped trying to align at boot time.
Thanks for the detailed explanation!
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