An anonymous reader sends this excerpt from the Opposable Thumbs blog:
"It doesn't take much raw power to play Nintendo or SNES games on a modern PC; emulators could do it in the 1990s with a mere 25MHz of processing power. But emulating those old consoles accurately — well, that's another challenge entirely; accurate emulators may need up to 3GHz of power to faithfully recreate aging tech. ... As an example, compare the spinning triforce animation from the opening to Legend of Zelda on the ZSNES and bsnes emulators. On the former, the triforces will complete their rotations far too soon as a result of the CPU running well over 40 percent faster than a real SNES. These are little details, but if you have an eye for accuracy, they can be maddening. ... The primary demands of an emulator are the amount of times per second one processor must synchronize with another. An emulator is an inherently serial process. Attempting to rely on today's multi-core processors leads to all kinds of timing problems. Take the analogy of an assembly line: one person unloads the boxes, another person scans them, another opens them, another starts putting the item together, etc. Synchronization is the equivalent of stalling out and clearing the entire assembly line, then starting over on a new product. It's an incredible hit to throughput. It completely negates the benefits of pipelining and out-of-order execution. The more you have to synchronize, the faster your assembly line has to move to keep up."