From: MARSHALL K. <Kei...@to...> - 2003-10-13 15:23:59
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Shiming Dong wrote: >I want to fetch the system time with the accuracy of micro - seconds, Does any time function in the mingw provide such accuracy? Presumably you mean the PC system time? This is updated by a hardware metronome which beats, on average 18.2 times per second, so even if you find a function which claims microsecond accuracy, it will not achieve it. Regards, Keith |
From: MARSHALL K. <Kei...@to...> - 2003-10-13 16:24:16
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Justin Forest wrote: >VOID WINAPI GetSystemTime(LPSYSTEMTIME); > >Returns milliseconds; see winbasee.h for details. But, given the accuracy of the underlying timing hardware, the accuracy of this is still no better than +/- 50 ms. Regards, Keith. |
From: Nicolas W. <nic...@gm...> - 2003-10-14 15:14:14
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>But, given the accuracy of the underlying timing hardware, >the accuracy of this is still no better than +/- 50 ms. > > Are you sure about that? I believe there are high accuracy timers on modern boards (they are somewhat needed for video replay)... Nico |
From: MARSHALL K. <Kei...@to...> - 2003-10-14 15:58:07
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>>But, given the accuracy of the underlying timing hardware, >>the accuracy of this is still no better than +/- 50 ms. > > >Are you sure about that? I believe there are high accuracy timers on >modern boards (they are somewhat needed for video replay)... Certainly, the video controller will have its own timing circuitry, but AFAIK the time of day clock is still dependent on the CMOS ROM BIOS clock, which, in order to support legacy software, still updates at the INT 8 frequency of 182 beats per ten seconds, i.e. (very) approximately one update every 50ms. Regards, Keith. |
From: Gisle V. <gv...@br...> - 2003-10-14 16:18:39
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"MARSHALL Keith" <Kei...@to...> said: > Certainly, the video controller will have its own timing circuitry, > but AFAIK the time of day clock is still dependent on the CMOS > ROM BIOS clock, which, in order to support legacy software, still > updates at the INT 8 frequency of 182 beats per ten seconds, i.e. > (very) approximately one update every 50ms. Where have you been the last 5+ years? Windows have supported RDTSC timebased counters and events since NT 3.1. Refer the libwinmm.a/winmm.lib library. timeGetSystemTime() returns system-time, while timeSetEvent() creates a oneshot/repetitive timer event at 1 msec resolution. I'd be amased if Windows uses the RTC for anything but getting the time during boot. --gv |
From: Schuster, J. (N-Compaq) <joe...@lm...> - 2003-10-14 17:35:25
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http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/timers/abouttimers.asp QueryPerformanceFrequency w/ QueryPerformanceCounter These give values that are hardware dependant. Depending on how the hardware handles these requests. These may give resolution to 50,000 counts per second. All other Windows based timing is actually +/- 10 ms. -----Original Message----- From: min...@li... [mailto:min...@li...]On Behalf Of Nicolas Weber Sent: Tuesday, October 14, 2003 5:29 AM To: min...@li... Subject: Re: [Mingw-users] question about time >But, given the accuracy of the underlying timing hardware, >the accuracy of this is still no better than +/- 50 ms. > > Are you sure about that? I believe there are high accuracy timers on modern boards (they are somewhat needed for video replay)... Nico ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. SourceForge.net hosts over 70,000 Open Source Projects. See the people who have HELPED US provide better services: Click here: http://sourceforge.net/supporters.php _______________________________________________ MinGW-users mailing list Min...@li... You may change your MinGW Account Options or unsubscribe at: https://lists.sourceforge.net/lists/listinfo/mingw-users |
From: Schuster, J. (N-Compaq) <joe...@lm...> - 2003-10-14 17:36:32
|
This call, timeGetSystemTime does document the resolution at 1 millisecond resolution. But you will see that you only ever get tens of milliseconds from it. You will never see a differentiation from say 10 to 11. Only 10 to 20. Just a note... -----Original Message----- From: min...@li... [mailto:min...@li...]On Behalf Of Gisle Vanem Sent: Tuesday, October 14, 2003 10:18 AM To: min...@li... Subject: Re: [Mingw-users] question about time "MARSHALL Keith" <Kei...@to...> said: > Certainly, the video controller will have its own timing circuitry, > but AFAIK the time of day clock is still dependent on the CMOS > ROM BIOS clock, which, in order to support legacy software, still > updates at the INT 8 frequency of 182 beats per ten seconds, i.e. > (very) approximately one update every 50ms. Where have you been the last 5+ years? Windows have supported RDTSC timebased counters and events since NT 3.1. Refer the libwinmm.a/winmm.lib library. timeGetSystemTime() returns system-time, while timeSetEvent() creates a oneshot/repetitive timer event at 1 msec resolution. I'd be amased if Windows uses the RTC for anything but getting the time during boot. --gv ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. SourceForge.net hosts over 70,000 Open Source Projects. See the people who have HELPED US provide better services: Click here: http://sourceforge.net/supporters.php _______________________________________________ MinGW-users mailing list Min...@li... You may change your MinGW Account Options or unsubscribe at: https://lists.sourceforge.net/lists/listinfo/mingw-users |
From: Shiming D. <do...@ya...> - 2003-10-13 15:28:45
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Yes, but I want to make it as accurate as possible. And the funtion of localtime( ) can only reach the precision of 1 second. I want a more accurate one. Do you have any idea? Thank you! shiming MARSHALL Keith <Kei...@to...> wrote: Shiming Dong wrote: >I want to fetch the system time with the accuracy of micro - seconds, Does any time function in the mingw provide such accuracy? Presumably you mean the PC system time? This is updated by a hardware metronome which beats, on average 18.2 times per second, so even if you find a function which claims microsecond accuracy, it will not achieve it. Regards, Keith ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. SourceForge.net hosts over 70,000 Open Source Projects. See the people who have HELPED US provide better services: Click here: http://sourceforge.net/supporters.php _______________________________________________ MinGW-users mailing list Min...@li... You may change your MinGW Account Options or unsubscribe at: https://lists.sourceforge.net/lists/listinfo/mingw-users --------------------------------- Do you Yahoo!? The New Yahoo! Shopping - with improved product search |
From: Justin F. <vh...@us...> - 2003-10-13 15:40:30
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Shiming Dong wrote: > Yes, but I want to make it as accurate as possible. And the funtion of > localtime( ) can only reach the precision of 1 second. I want a more > accurate one. Do you have any idea? VOID WINAPI GetSystemTime(LPSYSTEMTIME); Returns milliseconds; see winbasee.h for details. |