8 Mhz is Internal Clock, 12 | Microcontroller › AVR › avr usb programmer › 8 Mhz is Internal Clock, 12 September 6, 2012 at 7:38 am #8538 Manicka Raja PLParticipant 8 Mhz is Internal Clock, 12 Mhz is External Clock produced by Crystal Oscillator.