Re: [stella] 2600 emu for GBA

Subject: Re: [stella] 2600 emu for GBA
From: Julian Squires <tek@xxxxxxx>
Date: Wed, 27 Jun 2001 14:20:05 -0230
On Wed, Jun 27, 2001 at 10:30:08AM -0400, John Matthews wrote:
> So is my interpretation of what Otaku's emu does off base? That is, is
> it an emulator that tries to "interpret" the code and do the right thing
> instead of actually emulating each chip of the original hardware? (As in
> the N64 emu example.) Or does it do something else?

I think the divisions you're making might be a little off-base.

There are two major schools of emulation, interpretation and recompilation
(and two major divisions of recompilation, static and dynamic). You
have to understand what's going on in the system (that is, emulate
each chip of the original) in either case.

Most emulators use interpretation, as this is the most straight-forward
way of doing things from a programming standpoint. You could think of it
as very fine-grained dynamic recompilation, actually. The overhead involved
is quite high, though.

Recompilation involves rewriting the original code so that it can be
run on the native processor, without the interpretive overhead (of course,
there will be an interpretive element in how graphics are done and such).
Static recompilation means that it's done on startup, while dynamic
recompilation means doing it on the fly, which is sort of a compromise
between interpretation and static recompilation.

The page sounds pretty correct, btw -- I am continually impressed with
what the GBA can do... unfortunately it has pushed me to further delay
doing a 2600 project because of all the interesting work I'm now doing
on it. People have been looking at emulators only in terms of raw CPU
horsepower... this is a bit of a PC-centric view, because while in the
PC world you pretty much have to depend on the CPU for most things,
console systems have a lot of nifty extra hardware (as we're all familiar
with even from the 2600) that can take the load off an emulator, especially
an emulator for another console.

 |/|  Julian Squires <tek@xxxxxxx>

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