Bug report with RetroArch 0.97.1
1 - FCEUmm (or whatever it's called) - save states do not function, as in, no saves are created or loaded
Certain mappers currently have non-working savestate support (some games I know off the top of my head are Duck Tales, Mega Man 1, Super Mario Bros 1 - NROM-based mapper I believe) - this is known about and is in the libretro-cores README file. Problem is that FCEUmm lacks some patches that were implemented in FCEUX to address certain endian issues/mapper issues, so I have to backport patches from FCEUX from time to time.
I still prefer to use FCEUmm as a base because it has better mapper support, is faster and doesn't have all the TAS junk that FCEUX does. It's just a matter of ironing out those few bugs.
Also, I see that I'm lagging quite a few revisions behind when compared to the current FCEUmm trunk - commit 94 says:
Hopefully fixed all savestates now. (note to me: DO NOT SET STATE NAMES LONGERTHAN 4 SYMBOLS!) (TODO: make saves more flexible'
So hopefully when I'll update the libretro port to the latest version this weekend most of these issues will be gone.
I'll also try to get libretro support pushed upstream.