In some games the emulation of the CPU speed is incorrect, resulting in slowdown even if your game is running at a constant 60fps. This is definitely the case with Raiden as I recently played the arcade and it did not slow down any near as much as it does in MAME. Other games I've noticed with worse slowdown than the arcade are Double Dragon, Renegade and Chelnov.(posted 8978 days ago)cheat.dat and some versions of MAME allow you to overclock the CPU in the tilde menu, this can alleviate the slowdown however it's probably illegal to use overclocking in a MARP submission.