As it says on the title. I've started experiencing this after updating to 3.5 and then replacing SimpleDeckyTDP with Handheld Daemon.
When connected to a power source (even on one that doesn't deliver enough to actually charge the device!) the performance is alright.
But when I'm playing on battery / unplugged, games would have "hitches" once in a while. I've noticed that the power consumption in watts would drop to bare minimum and the clock speeds would be on the baseline before jumping back up to an acceptable number.