Re: Timer resolution
- From: "Arkady Frenkel" <arkadyf@xxxxxxxxxxxxxxxx>
- Date: Thu, 22 Sep 2005 09:32:50 +0200
You can set resolution to 1 mscek with Multimedia Timers(
timeBeginPeriod()/timeEndPeriod()) in desktop windows but that will not be
stable 1 msec so the better way to receive such is to use RT os like windows
CE where default resolution is 1 msec and not
10(15) as in desktop , obviously you can change that too if you build your
own BSP.
Arkady
"GrahamH" <pknvdw@xxxxxxxxxxxxx> wrote in message
news:8sRXe.8210$1A.1767@xxxxxxxxxxxxxxxxxxxxxxx
>
> <440gtx@xxxxxxxxx> wrote in message
> news:1127204725.482902.239760@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>> Do multiprocessor machines really use rdtsc for
>>>> KeQueryPerformanceCounter?
>>>
>>> Yes. Actually, any machine with a multiprocessor HAL
>>
>> Do you by chance know how power management is handled where the CPU
>> clock is reduced or increased? It seems there are two ways to go. Do
>> the units change (i.e. PerformanceFrequency returned from
>> KeQueryPerformanceCounter) or does it internally keep the units the
>> same by interpolating the rdtsc value? And unless each power level
>> transition happens at exactly the same instant on every cpu it seems
>> like different processors could start getting out of rdtsc step in a
>> hurry.
>>
>
> Thanks for all the input so far, but I'm still not clear how best to get
> real GMT time to 1ms resolution.
>
> I would still love to know what to expect of KeQueryInterruptTime, 1ms,
> 100us, 100ns ?? "Suitable for fine-grained timing" says MSDN! And how best
> to get real system time with 1ms resolution (my real goal). I have
> something running now that calls KeQuerySystemTime and
> KeQueryPerformanceCounter once when the driver first completes a frame
> capture. Thereafter it calculates the time interval from initialisation to
> now using KeQueryPerformanceCounter and adds this value, scaled to 100ns
> units, to the initial system time. But can I be sure that my clock will
> stay in-synch with system time over long periods? I can detect a loss of
> synch and re-initialise but that will cause a glitch in my frame to frame
> timing. I also have the inconvenience of dividing the count by the
> frequency and scaling to 100ns units. That needs more than 64 bit integer
> arithmetic.
> It looks like it might be better to increase the system tick rate to 1kHz
> with ExSetTimerResolution. Then any KeQuerySystemTime call will give me
> the desired resolution directly (I assume). But I don't really want all
> timer activity to increase tenfold.
>
> Help!
>
> Graham
>
.
- References:
- Timer resolution
- From: GrahamH
- Re: Timer resolution
- From: Tim Roberts
- Re: Timer resolution
- From: Tim Roberts
- Re: Timer resolution
- From: Pavel A.
- Re: Timer resolution
- From: Tim Roberts
- Re: Timer resolution
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