char canRenderFrame = 0;
char elapsedTicks = 0;

void far (interrupt *oldTimer());

void far interrupt timerInterrupt() {
  _disable();

  elapsedTicks++;
  if (elapsedTicks > SOME_THRESHOLD_FOR_30FPS) {
    canRenderFrame = 1;
    elapsedTicks = 0;
  }

  oldTimer();

  int(0x20, 0x20);
  _enable()
}