So, I wanted to play some snes9x on my mac mini. It's hooked up to a tv via hdmi; and every time I start/stop a game, it switches the hdmi output and overscans

So, I wanted to play some snes9x on my mac mini. It's hooked up to a tv via hdmi; and every time I start/stop a game, it switches the hdmi output and overscans like crazy. I still can't figure out whats going on with it. Anyone experience similar with hdmi output?