While technically correct for longer time frames, setting a performance governor on both windows and linux basically means that it comes out of idle at the max

While technically correct for longer time frames, setting a performance governor on both windows and linux basically means that it comes out of idle at the max allowable frequency. In order to achieve this it basically means that idle isn't adjusting the clock rates (to avoid the transition latencies) for idle times less than 2x those latencies. Depending on the core/firmware/etc it may be gating the clock, or clock skipping, which can save some power And yes it can waste energy you can measure with the your battery monitor (or UPS/PDU) but its also possible to measure the interrupt handling latency/etc, and for some cores it can make a very noticeable difference to desktop latency if you happen to be sensitive to such things. While I've posted elsewhere about clamping the clock rate to save power, I also do the converse when plugged in by cutting off the bottom 2/3rds of the frequency range. This results in a far more responsive desktop in linux and even windows to a lesser extent.