After a few recompiles and optimizations I think mame64's running about as fast as I can get it on my 12.04 system (about 7 times faster than it ran originally). Unfortunately, for e.g. pacman that's still about 5 times slower than it runs under Windows 7 (about 700% on Linux vs 3500% on Windows 7, the same dual boot system). That makes many of the later games still unplayable under Linux while they run fine under Windows 7. Anyone willing and able to help me figure out what the cause for this difference is?