Clock resolution ( and hence measuring elapsed time) does not depend
on interrupts per second.
Clock interrupts are another concept which is important when you need
system supplied callbacks at specific times.
| Norbert Kawulski | mailto:xxxxx@stollmann.de |
| Stollmann T.P.GmbH, Development | http://www.stollmann.de |
–If it’s ISDN or Bluetooth, make sure it’s driven by Stollmann–
“Behind every successful man stands a surprised mother-in-law.”
I hate to break the news to everyone, but just because the Operating
System has the possibility to keep time in 100nsec increments, that
does NOT mean the closk resolution is that fine. I believe that PCs
have clocks that interrupt every 1 millisecond (at least as WinNT
sets them).
The clock tick count is the minimum true resolution that can be
used. I suspect that some systems have clock rates that are settable
to something less that 1msec, and that an industrious system programmer
could change the resolution. The issue of clock resolution has to do
with whether or not you want to service that number of interrupts required.
I am sure you could buy a clock board that can interrupt faster than
every 1msec and write a driver to service those requests if you have
such a need.
just my opinion, Rick Cadruvi…
> -----Original Message-----
> From: xxxxx@lists.osr.com
> [mailto:xxxxx@lists.osr.com]On Behalf Of xxxxx@nai.com
> Sent: Wednesday, June 27, 2001 8:56 PM
> To: NT Developers Interest List
> Subject: [ntdev] Re: Clock resolution on a PC and WinNT
>
>
> Have you tried NdisGetCurrentSystemTime ??
> It has a 100-nanosecond granularity.
>
>
>
> >Hi, guys!
> >
> >I have a question (as always…). This time I believe it’s quite
> >simple:
> >
> >I’ve developed a driver that listens to the network card. For every frame
> >that
> >passes through the NIC, I’d like to record its timestamp.
> >
> >Currently, I use the KeQuerySystemTime() function in order to get it.
> >
> >The problem is that the resolution of this clock is not fine enough, and
> I
> >get the very
> >same timestamp for subsequent frames.
> >
> >I’ve been told by someone that there’s another way to get the time,
> >>using a special register that holds the real-time clock, and is updated
> >automatically, regardless of CPU state.
>
> >Is it true?
>
> Any suggestions?
>
> BTW: I’ve noticed that Linux has a clock with 1 microsecond resolution !
>
>
> thanks in advance,
>
> - Barak
>
>
>
> —
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