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/*
* tclWinTime.c --
*
* Contains Windows specific versions of Tcl functions that
* obtain time values from the operating system.
*
* Copyright 1995-1998 by Sun Microsystems, Inc.
*
* See the file "license.terms" for information on usage and redistribution
* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
* RCS: @(#) $Id: tclWinTime.c,v 1.8.8.1 2002/02/05 02:22:05 wolfsuit Exp $
*/
#include "tclWinInt.h"
#define SECSPERDAY (60L * 60L * 24L)
#define SECSPERYEAR (SECSPERDAY * 365L)
#define SECSPER4YEAR (SECSPERYEAR * 4L + SECSPERDAY)
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/*
* tclWinTime.c --
*
* Contains Windows specific versions of Tcl functions that
* obtain time values from the operating system.
*
* Copyright 1995-1998 by Sun Microsystems, Inc.
*
* See the file "license.terms" for information on usage and redistribution
* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
* RCS: @(#) $Id: tclWinTime.c,v 1.8.8.2 2002/06/10 05:33:20 wolfsuit Exp $
*/
#include "tclWinInt.h"
#define SECSPERDAY (60L * 60L * 24L)
#define SECSPERYEAR (SECSPERDAY * 365L)
#define SECSPER4YEAR (SECSPERYEAR * 4L + SECSPERDAY)
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* in place of the real-time clock as a performance counter
* reference. This results in:
* - inconsistent results among the processors on
* multi-processor systems.
* - unpredictable changes in performance counter frequency
* on "gearshift" processors such as Transmeta and
* SpeedStep.
* There seems to be no way to test whether the performance
* counter is reliable, but a useful heuristic is that
* if its frequency is 1.193182 MHz or 3.579545 MHz, it's
* derived from a colorburst crystal and is therefore
* the RTC rather than the TSC. If it's anything else, we
* presume that the performance counter is unreliable.
*/
if ( timeInfo.perfCounterAvailable
&& timeInfo.curCounterFreq.QuadPart != (LONGLONG) 1193182
&& timeInfo.curCounterFreq.QuadPart != (LONGLONG) 3579545 ) {
timeInfo.perfCounterAvailable = FALSE;
}
/*
* If the performance counter is available, start a thread to
* calibrate it.
*/
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* in place of the real-time clock as a performance counter
* reference. This results in:
* - inconsistent results among the processors on
* multi-processor systems.
* - unpredictable changes in performance counter frequency
* on "gearshift" processors such as Transmeta and
* SpeedStep.
*
* There seems to be no way to test whether the performance
* counter is reliable, but a useful heuristic is that
* if its frequency is 1.193182 MHz or 3.579545 MHz, it's
* derived from a colorburst crystal and is therefore
* the RTC rather than the TSC.
*
* A sloppier but serviceable heuristic is that the RTC crystal
* is normally less than 15 MHz while the TSC crystal is
* virtually assured to be greater than 100 MHz. Since Win98SE
* appears to fiddle with the definition of the perf counter
* frequency (perhaps in an attempt to calibrate the clock?)
* we use the latter rule rather than an exact match.
*/
if ( timeInfo.perfCounterAvailable
/* The following lines would do an exact match on
* crystal frequency:
* && timeInfo.curCounterFreq.QuadPart != (LONGLONG) 1193182
* && timeInfo.curCounterFreq.QuadPart != (LONGLONG) 3579545
*/
&& timeInfo.curCounterFreq.QuadPart > (LONGLONG) 15000000 ) {
timeInfo.perfCounterAvailable = FALSE;
}
/*
* If the performance counter is available, start a thread to
* calibrate it.
*/
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