Obtain the CPU speed, more accurate

I used to publish an article "roughly estimate the CPU speed" to get the CPU speed, but it is not very accurate. This time I released a relatively accurate program. The principle is exactly the same, but sleep is replaced by a high-precision counter.

# 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 ());
}

Original Author: nowcan
Origin: http://nowcan.yeah.net