The version number is highly specific. While modern PCs run much newer versions of MAME, this specific build is the gold standard for MAME4droid on Android and various "Lite" versions of emulators used on low-spec handhelds. Why 0.139u1? Stability: It is optimized for mobile ARM processors.
: Metal Slug 6 is an Atomiswave game. In MAME 0.139u1, emulation for this system is often slow or experimental . Users frequently report low frame rates (10–15 FPS) on older mobile hardware. metal slug 6 mame 0.139u1 rom
Are you getting a specific when loading the ROM? The version number is highly specific
: The ROM for Metal Slug 6 compatible with MAME 0.139u1 can also be found through arcade game ROM repositories. Again, be cautious of the sources you use. metal slug 6 mame 0.139u1 rom