[ltp] Running without a battery?

[Daniel Kraus]

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mukesh agrawal wrote:
> On Wed, 14 Jan 2004, Dr. Jason Breitweg wrote:
> 
> > Yeah, that would be really cool if you could check that out.  How does
> > one tell if the CPU is running at a lower speed?
> Any program that just executes a CPU loop would work. bogomips is one such
> program, that might already be installed.
> 
> If not, something like the following should do the trick:
> 
> --- spin.c ---
> 
> main() {
> 	int i = 1E6;
> 
> 	while (i) --i;
> }
> --------------

Use the attached programm to get you current cpu speed.

Cheers,
	Daniel

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#include <stdio.h>
#include <sys/time.h>

__inline__ unsigned long long int rdtsc()
{
	unsigned long long int x;
	__asm__ volatile (".byte 0x0f, 0x31" : "=A" (x));
	return x;
}

main ()
{
	struct timezone tz;
        struct timeval tvstart, tvstop;
        unsigned long long int cycles[2]; /* gotta be 64 bit */
	unsigned int microseconds; /* total time taken */
	
	bzero(&tz, sizeof(tz));

	/* get this function in cached memory */
	gettimeofday(&tvstart, &tz);
	cycles[0] = rdtsc();
	gettimeofday(&tvstart, &tz);

	/* we don't trust that this is any specific length of time */
	sleep(1);
	
	cycles[1] = rdtsc();
	gettimeofday(&tvstop, &tz);
	microseconds = ((tvstop.tv_sec-tvstart.tv_sec)*1000000) +
		(tvstop.tv_usec-tvstart.tv_usec);

	printf("%f MHz processor.\n",
		(float)(cycles[1]-cycles[0])/microseconds);
}



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