Uberjack has released a new version of his Master System/Game Gear emulator for the PSP, heres whats new:
SMS Plus PSP now includes the Time Rewind feature I mentioned earlier. To enable it, map any button to ‘Special: Rewind’. The feature alone takes up 85% of PSP’s memory, and I’m unsure what ramifications this might have for certain configurations, but if you come across problems, let me know.
Approximately 20 seconds of recent gameplay is saved, and saving is done once every five frames.