Re: poor accuracy of multimedia timer

I have done some experiment on using a single and duo core PC. The single
core clocked 10ms and duo core clocked on 15ms. Anyway thanx again Bob
so nice to talk to someone who has the idea. Anyone knows?

Regards
Vin



"Bob Masta" wrote:

On Thu, 7 Aug 2008 00:22:00 -0700, =?Utf-8?B?VmluY2VudE8=?=
<VincentO@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

Hi Bob,

I finally solve it thanx to for your help. I appreciate that. Not many
people know what happen. Anyway would like to ask you one last thing.

The reason why all the timer functions and get system time functions other
than multimedia timer can achieve the best timing of 15ms is because the RTC
on the motherboard is set to 64Hz?

Regards,
Vincent


Well, I don't know exactly which timer Windows uses for this, but I
think you have the basic idea. It's not what is normally referred to
as the RTC, which is the battery-backed clock that keeps track of
time-of-day when your system is off. I suspect it is more likely the
main system timer, which counts a 1.18 MHz clock and is responsible
for running time-of-day interrupts. In the Good Old Days, this was
set to 55 msec (18 Hz) which was a full 64k count of ticks. But it
can be set to any smaller interval with about 850 nsec resolution.
I suspect that Windows NT and later just sets it to about 15 msec.
(It was the full 55 msec in Win9x.)

I haven't seen the exact time documented anywhere, but I've heard
that it matters whether you have a multi-core system. I've heard
values from 10 msec to 20 msec. I don't know of a way to read this
value from the system... anyone?

Best regards,



Bob Masta

DAQARTA v4.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
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Relevant Pages

  • Re: poor accuracy of multimedia timer
    ... than multimedia timer can achieve the best timing of 15ms is because the RTC ... I suspect that Windows NT and later just sets it to about 15 msec. ... Scope, Spectrum, Spectrogram, Sound Level Meter ...
    (microsoft.public.win32.programmer.mmedia)
  • Re: poor accuracy of multimedia timer
    ... than multimedia timer can achieve the best timing of 15ms is because the RTC ... message queue. ... Scope, Spectrum, Spectrogram, Sound Level Meter ...
    (microsoft.public.win32.programmer.mmedia)
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