[ntp:questions] Re: Windows timekeeping - sudden degradation - why?

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Thu Dec 8 20:31:26 UTC 2005


Maarten Wiltink wrote:
> "David J Taylor"
> <david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid>
> wrote in message
> news:SdYlf.4949$iz3.4800 at text.news.blueyonder.co.uk... [...]
>> - QuickTime Player running (not even playing a video), timer
>> resolution just under 1ms (about 960 us)
>
> Probably 1000 or 1024 Hz. Perhaps 1048.576 Hz but that sounds really
> unlikely. Odd that it would be slightly _faster_ than 1024 Hz; it
> should really lose ticks, not gain time. Perhaps it's supposed to be
> 1193 Hz but then it would be missing a horrendous proportion of ticks.
>
>
>> - QuickTime not running, timer resolution seems to step between
>> 15.6ms (approx) and 10.5ms.
>
> Probably 64 and 100 Hz. 64 Hz may be related to .Net. It matches the
> resolution I observed for System.DateTime.Now evaluation. 100 Hz is
> "the" clock resolution for NT as far as I know.
>
> Groetjes,
> Maarten Wiltink

Maarten,

Thanks for your comments.  Please don't take the fast time resolution as 
correct - I've only measured it approximately.  Let's call it "fast" and 
1ms.  I have no argument with it.

Before posting, I tried to find on the Internet what I had measured 
before, and couldn't.  I've now had another search and found that I 
previously reported: "On my own systems, Windows XP Pro has about 15.62ms 
resolution, Windows 2000 Server about 10.62ms, 2000 Professional 10.31ms." 
This was over three years ago, on Nov 28 2002, 8:27 am!

SysInternals also offer a program, and an article about the internal NT 
API (i.e. not the normal Windows API):

  http://www.sysinternals.com/Utilities/ClockRes.html

  http://www.sysinternals.com/Information/HighResolutionTimers.html

It woukd be interesting to know where this is set in the registry...

Cheers,
David 





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