function GetCPUSpeed: Double;
const
  DelayTime = 500; // measure time in ms
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 / (1000.0 * DelayTime);
end;
 
procedure TForm1.Button1Click(Sender: TObject);
begin
 Caption:=Format('%f MHz', [GetCPUSpeed]);
end;