function RdTSC : int64; register;
asm
  db $0f, $31
end;

function GetCyclesPerSecond : int64;
var
  hF, T, et, sc : int64;
begin
  QueryPerformanceFrequency(hF); // HiTicks / second
  QueryPerformanceCounter(T); // Determine start HiTicks
  et := T + hF; // (Cycles are passing, but we can still USE them!)
  sc := RdTSC; // Get start cycles
  repeat // Use Hi Perf Timer to loop for 1 second
    QueryPerformanceCounter(T); // Check ticks NOW
  until (T >= et); // Break the moment we equal or exceed et
    Result := RdTSC - sc; // Get stop cycles and calculate result
end;