I am new to PiMAME, I managed to launch a game (asterix) ... yeah ... :) But it seems that the game is slower than the normal about half the speed (sound and video), I tried another game and it is the same. I overclocked at 900MHz. Is there something I can do ?
Try MAME4ALL which is included in the latest version of PiMAME. Because MAME4ALL is based on an earlier version of MAME it requires less resources and produces better results with some games.
Are you running from within X-windows? If so, don't. Stella was really slow when I ran it from within X-windows. Booting to terminal (not X), then running Stella fixed the speed problem.