Get the first update to MAME 0.118 over at the Latest Release page. This major change this time around is an internally revamped tilemap system. A set of regression tests have already been done and things look pretty good, so I don't anticipate a lot of new bugs with the new code, but there will probably be a few things I missed. Make sure you read the top of tilemap.h (either in the source or in the online source when it is updated later today) for more detail on how the tilemap system works.