Вычисление тактовой частоты процессора

function GetCPUSpeed: double;
const
  DelayTime = 500; // время измерения в миллисекундах
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 // rdtsc
    mov TimerLo, eax
    mov TimerHi, edx
  end;
  Sleep(DelayTime);
  asm
    dw 310Fh // rdtsc
    sub eax, TimerLo
    sbb edx, TimerHi
    mov TimerLo, eax
    mov TimerHi, edx
  end;
  SetThreadPriority(GetCurrentThread, Priority);
  SetPriorityClass(GetCurrentProcess, PriorityClass);
  Result := TimerLo / (1000.0 * DelayTime);
end;

begin
  LabelCPUSpeed.Caption := Format('CPU speed: %f MHz', [GetCPUSpeed]);
end;