The only time I've had to use overdumped ROMs has been recently, to make SuFami Turbo games work on SNES emulators and SD2SNES flashcart. For any reason, they require fusing 4x SuFami Turbo BIOS + game ROM to work, and such files appear as [o1] ROM versions in the GoodSNES romset.
GoodNGPx v3.27 Romset, marked as '(PD)'.
That makes sense, and thanks for the info as I also have an SD2SNES. However, I find it odd that those are classified as overdumps, rather than something like NameOfGame+Bios or another indicator that it includes something useful, not just extra unused space from the end of the chip, or some kind of dumping error. Now makes me wonder what other ones are useful, as I thought an overdump was typically identical to the 'good' rom, but less verified and larger (for what I thought was no good reason, such as untrimmed DS roms). They should really indicate that better, but then they don't listen to me!
Edited by Hastor, Mon Aug 28, 2017 4:02 PM.