program ....;
..
..


const
  ID_BIT = $200000; // EFLAGS ID bit

function GetCPUSpeed: Double;
const
  DelayTime = 500;
var
  TimerHi, TimerLo: DWORD;
  PriorityClass, Priority: Integer;
begin
  try
    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);
  except
  end;
end;


procedure TForm1.Button1Click(Sender: TObject);
var
  cpuspeed: string;
begin
  cpuspeed := Format('%f MHz', [GetCPUSpeed]);
  edit1.text := cpuspeed;
end;