It’s an old PC Xp desktop, nothing on it but Mach 3. The cpu usage goes from 16 to 35 percent. Sometimes I see a jump when it happens to 36 percent but not always. I don’t get this issue when I use the cnc usb program it came with. I’m using parellel cable with Mach 3, windows update is disabled no screen saver and PC never goes to sleep.