Programming Forums > Application Development > C++

saxman · Jan 24th, 2005, 3:16 PM

I'm trying to use the RDTSC (Read Time-Stamp Counter) x86 instruction in my C program. Now I have the instruction working... but I want to take the entire 64-bits and divide them by 400,900,000 (400.9M) to convert the cps rate into seconds in a floating-point format of some type. Then I want to display these seconds in a string using the PRINTF function. Can anyone offer some example code of how I might do this? The fact that the time-stamp is 64-bits long is what keeps throwing me for a loop since I'm obviously programming on a 32-bit platform.

saxman · Jan 30th, 2005, 2:38 PM

This comes from Ken Silverman:

(Toggle Plain Text)

#if 0 //To compile, type: "nmake getmhz.c"
getmhz.exe: getmhz.c; cl getmhz.c /MD /G6y /Ox /nologo /link /opt:nowin98
!if 0
#endif

#include <windows.h>
#include <stdio.h>

static __forceinline __int64 rdtsc64 () { _asm rdtsc }

void main ()
{
	__int64 q0, q1, t0, t1, qfrq;

	QueryPerformanceFrequency((LARGE_INTEGER *)&qfrq);

	QueryPerformanceCounter((LARGE_INTEGER *)&q0);
	t0 = rdtsc64();

	while (1) //Force at least a 1/32 second delay (use longer for more accuracy)
	{
		QueryPerformanceCounter((LARGE_INTEGER *)&q1);
		if (q1-q0 >= (qfrq>>5)) break;
	}

	QueryPerformanceCounter((LARGE_INTEGER *)&q1);
	t1 = rdtsc64();

	printf("Detected frequency: %.0fhz",((double)qfrq) * ((double)(t1-t0)) / ((double)(q1-q0)));

	getch();
}

#if 0
!endif
#endif

Problem solved.

Jan 24th, 2005, 3:16 PM	#1
saxman Newbie Join Date: Dec 2004 Posts: 7 Rep Power: 0	Using RDTSC In C/C++ I'm trying to use the RDTSC (Read Time-Stamp Counter) x86 instruction in my C program. Now I have the instruction working... but I want to take the entire 64-bits and divide them by 400,900,000 (400.9M) to convert the cps rate into seconds in a floating-point format of some type. Then I want to display these seconds in a string using the PRINTF function. Can anyone offer some example code of how I might do this? The fact that the time-stamp is 64-bits long is what keeps throwing me for a loop since I'm obviously programming on a 32-bit platform.

Jan 30th, 2005, 2:38 PM	#2
saxman Newbie Join Date: Dec 2004 Posts: 7 Rep Power: 0	Re: This comes from Ken Silverman: (Toggle Plain Text) #if 0 //To compile, type: "nmake getmhz.c" getmhz.exe: getmhz.c; cl getmhz.c /MD /G6y /Ox /nologo /link /opt:nowin98 !if 0 #endif #include <windows.h> #include <stdio.h> static __forceinline __int64 rdtsc64 () { _asm rdtsc } void main () { __int64 q0, q1, t0, t1, qfrq; QueryPerformanceFrequency((LARGE_INTEGER )&qfrq); QueryPerformanceCounter((LARGE_INTEGER )&q0); t0 = rdtsc64(); while (1) //Force at least a 1/32 second delay (use longer for more accuracy) { QueryPerformanceCounter((LARGE_INTEGER )&q1); if (q1-q0 >= (qfrq>>5)) break; } QueryPerformanceCounter((LARGE_INTEGER )&q1); t1 = rdtsc64(); printf("Detected frequency: %.0fhz",((double)qfrq) * ((double)(t1-t0)) / ((double)(q1-q0))); getch(); } #if 0 !endif #endif #if 0 //To compile, type: "nmake getmhz.c" getmhz.exe: getmhz.c; cl getmhz.c /MD /G6y /Ox /nologo /link /opt:nowin98 !if 0 #endif #include <windows.h> #include <stdio.h> static __forceinline __int64 rdtsc64 () { _asm rdtsc } void main () { __int64 q0, q1, t0, t1, qfrq; QueryPerformanceFrequency((LARGE_INTEGER )&qfrq); QueryPerformanceCounter((LARGE_INTEGER )&q0); t0 = rdtsc64(); while (1) //Force at least a 1/32 second delay (use longer for more accuracy) { QueryPerformanceCounter((LARGE_INTEGER )&q1); if (q1-q0 >= (qfrq>>5)) break; } QueryPerformanceCounter((LARGE_INTEGER )&q1); t1 = rdtsc64(); printf("Detected frequency: %.0fhz",((double)qfrq) * ((double)(t1-t0)) / ((double)(q1-q0))); getch(); } #if 0 !endif #endif Problem solved.

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Programming Forums > Application Development > C++

Using RDTSC In C/C++