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Date: Fri, 02 Mar 2001 18:06:05 +0100
From: Manfred Spraul <manfred@colorfullife.com>
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CC: linux-kernel@vger.kernel.org
Subject: Re: strange nonmonotonic behavior of gettimeoftheday
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>
> on AMD K6, VIA Technologies VT 82C586, Compaq Presario XL119. 
> [snip]
> gives following result on box in question 
> root@******:# ./clo 
> Leap found: -1687 msec 
> and prints nothing on all other my boxes. 

Perhaps APM or SMI problems?
Could you run the attached program?

--
	Manfred
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#include <stdio.h>
#include <sys/time.h>
#include <unistd.h>
#include <time.h>

static unsigned long long get_tsc(void)
{
    	unsigned long v1;
	unsigned long v2;
	__asm__ __volatile__(
		"rdtsc\n\t"
		: "=a" (v1), "=d" (v2));
	return (((unsigned long long)v2)<<32)+v1;
}

int main(int argc, char** argv)
{
	unsigned long long t1;
	unsigned long long t2;

	printf("RDTSC tester\n");
	t1 = get_tsc();
	for(;;) {
		t2 = get_tsc();
		if(t1 > t2) {
			printf("tsc jumped backwards: from %lld to %lld.\n",
					t1, t2);
		}
#if 0
		printf("diff is %lld-%lld=%d.\n",t2,t1,t2-t1);
#endif
		t1 = t2;
	
	}
	return 1;
}


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