Garrison72: I did try it. Unintuitive UI but looks great. Although I don't understand why it would take a beefy machine to emulate NES games. It must push the processor? My i7, 3.50 GHz CPU seems to do the job.
SirPrimalform: The more accurate the emulation, the more the processing costs spiral out of control. Getting the timing *exactly* right requires heaps of power just because of the fine level of synchronisation between the emulated processors. Quick emulators generally make do with simplifying the timing and then coming up with hacks and patches to stop games from crashing.
Example of inaccurate emulation:
The Super NES's sound chip uses a buffer for its echo effects. When the echo effect is used, the sound chip writes the data into an area of RAM for later mixing. This, of course, works only if the echo buffer size is reasonable.
However, ZSNES (and I believe older versions of SNES9x) did not emulate that aspect of the DSP. Hence, a buffer size that is impossible on real hardware would not crash the game, even though it would crash on real hardware. Basically, ZSNES, rather than simulating the sound chip, would take a shortcut to yield audio without emulating the entire chip.
bsnes, however, does simulate the sound chip. This takes more CPU because it's actually emulating an extra CPU, but results in more accurate emulation, causing romhacks that set the buffer size too large to crash.
(I wonder if a game could detect ZSNES by setting an echo buffer size, using it, and checking to see if data actually got written there. Of course, ZSNES has a bug with, I believe, a BCD instruction yielding the wrong result, which can also be used to detect it,)