Mac OS X 10.2.5 or later
QuickTime 6.4 or later
PowerPC G3 300MHz or later
G-Force/ATI Rage 128 or later for OpenGL support
Certain games use added hardware which will require a faster Mac. The specs listed above is the MINIMUM to use Snes9x in any playable form. Most people will not even find that playable. It is recommended that you get a semi-modern Mac with a 800MHz PowerPC processor if you want good results. A 1GHz PowerPC or Intel Mac is recommended for those that want a near perfect experience. Also 64MB of RAM is highly suggested with the possibility of more being needed if you play a game that requires Graphic Packs.
You will need access to SNES ROM images in .smc, .sfc, .fig, etc., format otherwise you will have nothing to run!
Some home-brewed ROM images can be downloaded from http://www.zophar.com/.
Please note, it is illegal in most countries to have commercial ROM images without also owning the actual SNES ROM cartridges.