so i load the dat, go to rebuilder, select dirs of old and new roms, and do a rebuild, right?

> > won't it try to rebuild all the roms?
>
> No. The diffdat only contains the definitions for the difference of two dats.
> Use Logiqx' tools or his prepared dats for each mamerelease.
>
>
> Roman Scherzer
> ClrMamePro
>