得到CPU的速度，較精確

以前發布過一篇文章《粗數量級估計CPU的速度》可以得到CPU的速度，但是不是很准，這次發布一個比較準的程式。原理完全一樣，只是用高精度計數器代替了Sleep。

#include
#include

int __fastcall Frequence_MHz()
{
LARGE_INTEGER ulFreq, ulTicks, ulValue, ulResult;
__int64 ulEAX_EDX, ulStartCounter;
DWORD PriorityClass, Priority;

PriorityClass = GetPriorityClass(GetCurrentProcess());
Priority = GetThreadPriority(GetCurrentThread());

SetPriorityClass(GetCurrentProcess(), REALTIME_PRIORITY_CLASS);
SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);

// it is number of ticks per seconds
QueryPerformanceFrequency(&ulFreq);

// current valueofthe performance counter
QueryPerformanceCounter(&ulTicks);

// calculate one second interval
ulValue.QuadPart = ulTicks.QuadPart + ulFreq.QuadPart;

// read time stamp counter
// this asm instruction load the highorder 32 bit of the register into EDX
// and the lower order 32 bits into EAX
_asm {
rdtsc
mov DWORD PTR ulEAX_EDX, EAX
mov DWORD PTR (ulEAX_EDX + 4), EDX
}

// start no of ticks
ulStartCounter = ulEAX_EDX;

// loop for 1 second
do {
QueryPerformanceCounter(&ulTicks);
} while (ulTicks.QuadPart <= ulValue.QuadPart);

// get the actual no of ticks
_asm {
rdtsc
mov DWORD PTR ulEAX_EDX, EAX
mov DWORD PTR (ulEAX_EDX + 4), EDX
}

// calculate result
ulResult.QuadPart = ulEAX_EDX - ulStartCounter;

SetThreadPriority(GetCurrentThread(), Priority);
SetPriorityClass(GetCurrentProcess(), PriorityClass);

return (int)ulResult.QuadPart / 1000000;
}

int main()
{
printf("CPU speed = %d MHz/n",Frequence_MHz());
}

原作者：NowCan
來 源：http://nowcan.yeah.net