The Professor SF II is a backup unit (or "copier") for the Super Nintendo Entertainment System, and was manufactured by Bung Enterprises of Hong Kong, and is the American version of the Game Doctor 7. It is not usually considered to be the best back-up unit for the system, but for a while it was the most available, and hey, it allows you to play SNES ROMs on a real SNES (most of the time).
The PSF2 sports an incredibly loud floppy drive for copying and loading ROMs, an LPT1 port for hooking it up to your computer (which I incidentally could never get to work), built in routines which attempted to find and nuke copy protections, and Goldfinger cheat-code support. The unit also had the handy feature of allowing you to format disks to 1.6MB. You could play games with a mode that allowed you use the equivalent of "save states", although this was buggy and didn't work on some occasions. The unit usually came with 32Mbit of RAM, and was expandable to 128Mbit, but 32Mbit was big enough for almost every game released for the SNES, since Tales of Phantasia and Star Ocean were the only SNES games above 32Mbit in size. Games utilizing special chips like the DSP, SDD-1, FX, FX2, or C4 could not be played. Star Ocean used a custom chip, so the only game which would benefit from more RAM was Tales of Phantasia.
In my experience and from what I've heard of the experiences of others, the Professor SF II is, like many copiers, a little unreliable. It can black-screen when you start up, not load your games until you smack it around a bit, not recognize the existence of its own RAM, erase games from RAM at random, or its Save RAM support may stop working, thus not allowing you to save or load your games and losing any progress you made that wasn't backed up on disk. Most problems, however, seem to go away with time or by smacking the unit, much like the old toaster-style NESes.
The PSF2 was also infamous for an incredibly inane filename-format that the ROMs had to be formatted to on disk, which resulted in filenames like "SF32DKCA". The filename-format varied depending on the size of the ROMs and the amount of disks it needed to be split into, and took a time to get used to.
However, despite its weaknesses, the Professor SF2 is a way to play well over 95% of the SNES ROMs in existence on a real SNES, and as such is a very neat thing to have.
Thanks to malcster for pointing out that the Professor SF II's RAM could be upgraded to 128Mbit, not just 64Mbit as I previously stated. | 
