Determine CPU frequency

Here is just small piece of assembler code to determine CPU frequency in MHz.

function CPUSpeed: Double;
const DelayTime = 500;
var
  TimerHi, TimerLo: DWORD;
  PriorityClass, Priority : Integer;
begin
PriorityClass:=GetPriorityClass(GetCurrentProcess);
Priority:=GetThreadPriority(GetCurrentThread);
SetPriorityClass(GetCurrentProcess, REALTIME_PRIORITY_CLASS);
SetThreadPriority(GetCurrentThread, THREAD_PRIORITY_TIME_CRITICAL);
Sleep(10);
  asm
    dw 310Fh
    mov TimerLo, eax
    mov TimerHi, edx
  end;
  Sleep(DelayTime);
  asm
    dw 310Fh
    sub eax, TimerLo
    sbb edx, TimerHi
    mov TimerLo, eax
    mov TimerHi, edx
  end;
SetThreadPriority(GetCurrentThread, Priority);
SetPriorityClass(GetCurrentProcess, PriorityClass);
Result := TimerLo / (1000 * DelayTime);
end;

NOTE: NOT TESTED ON MULTICORE PROCESSORS