: Acquire ROMs legally. Some manufacturers and developers allow MAME users to use their ROMs if they own the original game, but others may not.
Cons
It looks like you’re referencing a specific version and a portable setup for Metal Slug 6 . metal slug 6 mame 0139u1 portable
Running MAME on a portable device or making MAME portable involves having the MAME software and ROMs on a removable storage device (like a USB flash drive). This way, you can play arcade games on any computer that supports MAME, without needing to install anything. : Acquire ROMs legally
: Standard MAME does not use hardware-accelerated rendering for 3D systems like the Atomiswave. On the 0.139u1 set, this often results in significant slowdowns or "unplayable" frame rates on most portable hardware. metal slug 6 mame 0139u1 portable