cpu 测速(mhz)和高精度延时(微秒级).txt

一．高精度延时, 是 CPU 测速的基础 Windows 内部有一个精度非常高的定时器, 精度在微秒级, 但不同的系统这个定时器的频率不同, 这个频率与硬件和操作系统都可能有关。 利用 API

一．高精度延时, 是 CPU 测速的基础

void DelayUs(__int64 Us)
{
    LARGE_INTEGER CurrTicks, TicksCount; 

    QueryPerformanceFrequency(&TicksCount);
    QueryPerformanceCounter(&CurrTicks); 

    TicksCount.QuadPart = TicksCount.QuadPart * Us / 1000000i64;
    TicksCount.QuadPart += CurrTicks.QuadPart; 

    while(CurrTicks.QuadPart<TicksCount.QuadPart)
        QueryPerformanceCounter(&CurrTicks);
}




二．测速程序
int CPU_Frequency(void) //MHz
{
    LARGE_INTEGER CurrTicks, TicksCount;
    __int64 iStartCounter, iStopCounter;

    DWORD dwOldProcessP = GetPriorityClass(GetCurrentProcess());
    DWORD dwOldThreadP = GetThreadPriority(GetCurrentThread());

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

    QueryPerformanceFrequency(&TicksCount);
    QueryPerformanceCounter(&CurrTicks);

    TicksCount.QuadPart /= 16;
    TicksCount.QuadPart += CurrTicks.QuadPart;

    asm rdtsc
    asm mov DWORD PTR iStartCounter, EAX
    asm mov DWORD PTR (iStartCounter+4), EDX

    while(CurrTicks.QuadPart<TicksCount.QuadPart)
        QueryPerformanceCounter(&CurrTicks);

    asm rdtsc
    asm mov DWORD PTR iStopCounter, EAX
    asm mov DWORD PTR (iStopCounter + 4), EDX

    SetThreadPriority(GetCurrentThread(), dwOldThreadP);
    SetPriorityClass(GetCurrentProcess(), dwOldProcessP);

    return (int)((iStopCounter-iStartCounter)/62500);
}
 

前面是用 API 函数进行延时, 如果知道了 CPU 的工作频率, 利用循环, 也可以得到高精度的延时

int _CPU_FREQ = 0; //定义一个全局变量保存 CPU 频率 (MHz)

void CpuDelayUs(__int64 Us) //利用循环和 CPU 的频率延时, 参数: 微秒
{
    __int64 iCounter, iStopCounter;

    asm rdtsc
    asm mov DWORD PTR iCounter, EAX
    asm mov DWORD PTR (iCounter+4), EDX

    iStopCounter = iCounter + Us*_CPU_FREQ;

    while(iStopCounter-iCounter>0)
    {
        asm rdtsc
        asm mov DWORD PTR iCounter, EAX
        asm mov DWORD PTR (iCounter+4), EDX
    }
}

void TestDelay(void)
{ 
    _CPU_FREQ = CPU_Frequency(); //利用 CPU 频率初始化定时
    CpuDelayUs(1000000); //延时 1 秒钟
}