General question about emulation

[Shonumi]

In addition to what's been said, sometimes it's also the case that one aspect isn't emulated at all, but it's such a small component that other parts of game don't rely on it, functionally speaking. A nice example on I personally encountered happened when I was emulating Pokemon Gold the other day. The intro has little waves in the ocean; they're supposed to move back and forth but my emu I'm writing didn't do that. Turns out I needed to implement a certain non-essential feature (HBlank STAT interrupts) to get that graphical effect.