Importantly, this doesn't use a lot of CPU or RAM. It just means creating a save state every second and keeping a log of all inputs.
Another simpler approach is to make an SNR for each frame and limit the RAM snapshot to 128KB, which is ok for 99% of CPC software. 128KB * 50 frames * 60 seconds = 384MB needed for the rewind functionality.
= Emulator accuracy checking tools =