For example, Nestopia is probably the most accurate emulator available to the original NES design, and requires anywhere from 800MHz to 1.5-1.6GHz of Intel x86 CPU power to properly emulate the equivalent of a TI graphing calculator. The developer of this has moved to SNES emulation (again, as close to the original as possible), and has found that he needs 3+GHz on an Intel platform to approach being proper emulation of the SNES hardware. That gaming console hardware was from 1990, and had hardware for CPU and audio that ran at ~21MHz. Again, the issue isn't speed, it's timing and accuracy - that hardware, while paltry in speed, was highly optimized to do what that device did. Emulating something from 1990 at about 21MHz takes upwards of 3GHz on today's hardware.... Interesting, no?