What Exactly is "Perfect Emulation"?

[zedrein]

Since I am such a huge fan of classic video game consoles I have often pondered what it would take to achieve (short of playing on the real hardware) a perfectly identical experience to the original game. I've read on some forums that to perfectly emulate a certain console, take the original NES for example, 1.5 GHz of computing power would be required. What I really wonder is this: is there even such a thing as "perfect" emulation? I mean, surely there will be some differences between the original hardware and emulating hardware in sound, gameplay, and video reproduction, right? Someone please clear this up for me!

[pandachromatic]

Philosophically speaking, I would say that perfect emulation is impossible. Simply because the controls are completely different with an emulator, which can take away from the experience. Also, save states and the like—for me—have lead to a completely different playing style.
That being said, i've used NES emulators on slower computers without any setbacks, so I doubt the 1.5GHz value has any real meaning.

[FatTrucker]

If an emulator exactly emulates the correct timing and function of every piece of hardware and software inside a console and will then run with a 1:1 output in framerate etc then there is no functional difference.
The closest any emulator has come to this so far is Bsnes which almost perfectly emulates every single hardware function of the Snes on a 1:1 basis.

There will always be minor differences, like control latency due to the PC interface you're using, differences in the visual integrity due to the type of display you're using etc, but in terms of the emulation output, 'perfect' emulation is attainable in terms of the emulator code.
In terms of computing power there are no specific rules you can attribute, recreating hardware functions in software is incredibly processor intensive, meaning PC's with specs way above the emulated machines hardware struggle to maintain a decent frame rate. With multiple core processors, 64 bit OS's and the use of functions in dedicated video hardware though, its becoming more and more credible to favour accuracy over hacks.
Generally Mame leads the way on this, what with it being an archival project with a focus on accuracy over playability.

[zedrein]

Very interesting! You see, I've never really found the video emulation for any of my favorite emulators to be problematic (except of course the fact that I am playing on a fixed-resolution LCD display instead of a low-resolution CRT) I just always thought the sound was a little off, leaving out the nuances that made the original system so great. I just hope that people continue to work at preserving these retro gems that I love so much, I'd hate to see any of these systems disappear into obscurity!