Differences between the models?

[Metal_Sonic]

I know there is two different models(US consoles) but all I know ls that the differences are cosmetic(Oval/Round buttons). I think the numbers are M-80000 and M-80000A. Is there something different between them or are the differences purely cosmetic?

[chizzles]

As far as the functionality goes, they are both the same.

However there are different motherboard designs that make modding certain revisions harder.

Some of the Japanese consoles, generally those manufactured from the "This is cool!" Skeleton Saturn and onwards, actually have compatability issues with some games.

[termis]

I don't know the model numbers, but of the ones I've seen (mostly US models, but I believe they're pretty much the same as PAL & standard issue Japanese units).

Mk I (oval button) units
1) 1st revision -- with power supply unit attached to the top half of the unit.
2) 2nd revision -- with psu on the bottom half of the shell. I believe the laser assembly is identical to the first revision (if not, I know they're at least interchangeable).
3) 3rd revision -- psu on the bottom, has the 21-pin ribbons connecting the laser assembly with 64-pin IC on it. (Essentially, the laser units of the earliest round button models). Supposedly only built during April of 96.

Mk II (round button) units
4) internally the same as 3), but now has the new shell, and the drive access light has been taken out (though technically you can hack it back in yourself)
5) Motherboard revised from 4), uses the 32-pin IC on the laser assembly.
6) Can't recall how different the motherboard was, but the laser assembly is built by Sanyo, and there's a small daughterboard that connects between the laser assembly and the motherboard.

And I think that's about it for the Vanilla models of Saturns. I don't know too much about the licensed saturns or one-off saturns.