Not sure mate, as I understand it (and I don't really) the processor has what is called a suicide battery, once the battery dies there is a small amount of saved code that gets lost.
There is a work around where someone has reverse engineered the processor and they give you this plus some new eproms and bobs yer uncle.
Still haven't heard back from Sega Resurrection :(
Yeah I know, the roms are patched to run without the extra code, not sure if the MAME roms are patched so they can work with MAME.
I used MAME roms when I did the freeplay mod on my Outrun
