HPWM patchy

Using HPWM and int osc I am trying with a 648A to continuously rotate a servo slowly and smoothly while other things are going on. The result is pretty uneven (jerky) and my scope confirms that as leds flash etc the pulselength actually changes. Any suggestions ?

Show us your code and how you did connect the motor to the chip. Maybe you are making very much emc pulses on your powersupply.