Super Game Boy Color

[Waterbury]

How feasible would you say it would be to modify a Super Game Boy to play Game Boy Color games?

Before you flame me, I know it won't be as easy as overclocking a chip, but I'm interested in what somebody with experience with Game Boy hardware would have to say.

[kendrick]

Well, obviously a Super Game Boy would already be able to play the color games that are backward compatible to the older platform. But I'm guessing that what you want is to be able to display the full color palette through the SGB interface and on the TV as a result?

The short answer is, this is a software problem and not a hardware problem. It's not like you could swap in chips or other components from a GBC or GBA handheld unit and get that result, if that's indeed what you're after. The component of the SGB cart that feeds video through the SNES encoder would have to be reprogrammed to accept the wider bit definition of the color information for each pixel; the standard DMG color palette is only two bits (00, 01, 10, 11) whereas the GBC color palette is a full 8-bits if I remember correctly.

So theoretically, there's nothing to stop you from trying. But here on GamesX, software modification of this type is generally off-topic. There's no formal prohibition against talking about it, but I doubt the regulars here can be of much help.

[Waterbury]

I found the attached document, from Nintendo, which seems to indicate how to code for the GBC hardware.

http://www.start-game.com/files/gbcprimer.doc

[Waterbury]

Honestly, I'm more interested in the hardware aspect. Such as if the RAM chips were replaced, and if the Z80 were overclocked, would there be other problems? Original GB data bus not fast/wide enough? Would you be able to modify the architecture while not venturing off widely enough, that the SNES interface would still operate? Any timing issues? I know there has to be an expert or two on this forum that is as crazy as I.   

[l_oliveira]

I think the CGB CPU chip behaves differently (aka might have extra hardware registers that are used by games to identify it as a CGB) so it could be impossible to achieve what you want to.

[Waterbury]

I looked up some more information online. I understand what would be involved, and it would be difficult, but (possibly) feasible. I imagine it would involve interfacing a Game Boy Color Motherboard to the Super Game Boy control chip via video, audio, and control signals. You'd have to hack the SGB Rom to allow it to act normal for GB and SGB games, and to completely operate differently in GBC mode.

Despite this, I KNOW it would be HIGHLY difficult. I'll investigate more, and maybe in 2 years or so I'll come back around to it.