Emulators runs games faster VS Real Hardware?

Some emulators do not properly emulate hardware slow, or don't emulate it at all. Play the recent Cave SH3 games. The screen fills up w/ bullets and Mame doesn't skip a bit. This renders them "unplayable" to some.

 

A good emulator will not run a game faster than the real hardware, but on your average OS this is harder than you'd think to control. You have to rely on imprecise timers and high latency blitting functions which introduce jitter. Early emulators just use Vblank, which can be a relatively accurate, assuming games only update music once per frame, and the computer's Vblank is the same as the emulated target. But better emulators keep an accurate virtual timebase, and achieve perfect timing on AVERAGE by predicting latency and adjusting, that's the only way possible. They do this by emulating components with precise timing relative to eachother, then synchronizing them all (least common denominator) to either the highest performance system timer or the sound buffer.

Emulators can increase a game's speed by: not emulating CPU instructions with the correct timing, allowing the CPU more cycles (overclocking), not following the actual hardware's timing, not emulating video hardware with the correct timing (such as assuming 60 Hz refresh), or not synchronizing the components to an accurate time base.

 

Some arcade games weren't running at an average 60fps but emulated at 60fps by MAME
Comes in mind tetris the grand master 2 or street fighter third strike.
But meh, between 60 fps and 62 or 57, you need to be da real hardcore gamer to feel the difference.