A single oscillator frequency of 8MHz is offered in version 4.0. For later 4.x versions, two frequencies are offered: 4 and 8MHz for ATtiny2313, and 4.8 and 9.6MHz for the ATtiny13. The OSCCAL register is changed so that only seven bits are used to tune the frequency for the selected oscillator. The MSB is not used. Auto-loading of the default calibration value and system clock prescaler is present.