From: christopher diggins (cdiggins_at_[hidden])
Date: 2005-02-13 19:30:01
----- Original Message -----
From: "Martin Slater" <mslater_at_[hidden]>
> watch the line wrap. QueryPerformanceCounter uses the CPU clock and is not
> per task but system wide.
>> Can you point me to documentation which supports your assertion?
>>> The only problem with QueryPerformanceCounter() is that it can "jump"
>>> on some chipsets.
>> I believe this problem is perhaps not restricted to
>> QueryPerformanceCounter() but to any counter counting mechanism, as the
>> problem is at the chipset level not the API level.
> No, there is a very particualar problem relating to
> QueryPerformanceCounter() on some (old?) chipsets the can cause it go
> backwards in time and wrap after approximately 20 minutes. I reported this
> to microsoft some years ago and it was confirmed an issue. (at the time
> only happened to me on one particualar celeron / motherboard
> configuration). By backwards in time I mean you could call the counter in
> a loop and have a reported time earlier than one got the previous
Really? That is different than the issue documentation I found at
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q274323 which stats
that the QueryPerformanceCounter() can jump *ahead* a few seconds. I wonder
if the status of the issue has changed to this new version or the
documentation just sux.
> This bit me on commercial code and I resorted to
> instead with no issues.
Thanks for your help Martin,
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