It's worth pointing out that if you want to run MAME, specifically, RetroPie is a bad choice, as is using the Raspberry Pi in general.<p>MAME's architecture does not lend well to it being converted into a core. Several features get weakened, disabled, or broken, and they generally don't function the way they're supposed to, especially with respect to controller input.<p>The version of MAME available for RetroPie is considerably older and outdated. Many of the features have been altered or disabled in order to make MAME work on less powerful hardware.<p>Even a low end PC running the latest version of MAME (222, at the time of writing) is going to give you a much better experience.