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PostPosted: Sat Dec 27, 2008 1:22 pm 
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So, oddly with a system as big as Gameboy Color is, I can't seem to find any good documents about it. Everything I find is about the original Gameboy with some minor mentions of Color GameBoy, but absolutely no details on GameBoy Color additions like DMA, Extra VRAM, Toggling CPU Speed, etc.

Does anyone know where to get good and complete GBC information? It seems GB and GBC documentation can't compare to the NES documents that are available.


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PostPosted: Sat Dec 27, 2008 4:15 pm 
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IIRC, there wasn't much added for the GBC upgrade. Heh - but it's been a long time since I've touched GB/C dev. CPU speed, another bank of vram, an additional DMA mode or something. That's all I can remember. Anyway...

The GBColor cribsheet should give you the memory mapped registers you're looking for - http://pcedev.net/gbc/GBCribSheet000129.pdf . (Some GBC stuff on page 3)

Here's the original GB cribsheet in case... dunno.. here - http://pcedev.net/gbc/GBCribSheet.pdf .


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PostPosted: Sat Dec 27, 2008 7:26 pm 
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The GBC may not have added "much" but if it had a damned backlight it would have been quite a worthy improvement. More VRAM for more tiles, color, 2x CPU speed, DMA to VRAM. Not too shabby in my opinion.

I'd swear I'd seen that cribsheet before and it didn't have any of the register listings like the one you linked me here. I think I have the information I need now.


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PostPosted: Sat Dec 27, 2008 10:07 pm 
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I think this is a good source of info for GBC:

http://nocash.emubase.de/pandocs.htm

That's pretty much the only one I've ever seen. Recently I had the same issue looking for GBC docs.


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PostPosted: Sat Dec 27, 2008 10:55 pm 
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I updated a copy of that to include more complete SGB information at GSHI. A consequence of using the document to rip SGB game SPC files.

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PostPosted: Sun Dec 28, 2008 1:23 am 
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Thanks Celius for the link. That's much more informations than the previous "Pandocs" I'd seen. I get the feeling only versions of information is all about.


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PostPosted: Sun Dec 28, 2008 3:41 am 
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Yeah, no problem. I actually can't recall how I found that info. I think it was by luck. It's sad that there's so little info and basically not even ruins or fossils left by a GBCdev community. I don't even know if one existed. Well at least there's this little documentation, which is pretty much all you need to know (though there are probably hardware quirks that aren't documented, but oh well, I guess).


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PostPosted: Sun Dec 28, 2008 11:45 am 
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Well I think we are somewhat spoiled by how well documented the NES is now. It would be nice if GBC reached that level someday, same with SNES.

I think I have most of the information I need to get started, I can feel my way through the blurry parts.


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PostPosted: Sun Dec 28, 2008 4:11 pm 
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Interesting...


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PostPosted: Sun Dec 28, 2008 5:42 pm 
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I dabbled in b&w gameboy for a bit - made a calculator that has a working user interface and can convert BCD into a 40-bit number but is still non-functional. That was done in asm but I wanted to make an 8-way scrolling map using C. Then I noticed the compiler doesn't do 16-bit math so the heck with it.


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PostPosted: Tue Dec 30, 2008 11:31 pm 
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I still have lots of downloaded material/docs/etc from when the GBC dev scene was booming. There's *tons* of redundant info though. Everything you probably need to know is at the no$cash link.

It's too bad the PCE wasn't a little faster. I'd try to emulate the original GB :D

Who knows, I still might try it out for a game or two. After all - not all games use 100% cpu resource.


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PostPosted: Wed Dec 31, 2008 6:29 am 
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Game Boy has 8 KB of work RAM. Wikipedia says PCE has 8 KB of work RAM. Where would you put the state of the emulated machine? Would you try to shoehorn it into VRAM, given that it's dual ported?


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PostPosted: Wed Dec 31, 2008 8:42 am 
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One of the PCE ROM types has an additional 32k of ram. I'd use that configuration or put it into a CDROM project where it's all ram. The PCE has plenty of open bus areas in the upper 2meg range where I can easily map in some extra ram, but I doubt I can convince any PCE emulator authors to support it even if I have it setup and working on my rom board :( But now I'm getting off topic..


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PostPosted: Wed Dec 31, 2008 3:17 pm 
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There's tons of poorly documented obscure facts about the GBC, like how scanline 0 starts much eariler than you'd think it would, but if you tried to emulate it such that all scanlines took equal time, you'd end up with scrolling artifacts near the top of the screen in many games.

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PostPosted: Wed Dec 31, 2008 9:42 pm 
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That's what I'm doing though, trying to emulate it. However right now the issue is probably cpu core development and emulating registers to get games to run. Right now I got Dr. Mario partially running. But it's not running correctly yet. It'll be awhile till I figure out what the deal is with it. I seem to remember someone saying that GB was easier than the NES but I seriously think they are wrong. The NES was not near as difficult for me to start emulating. I've only been at the GB for a few days but I honestly didn't think I'd have this much trouble getting simple games working.


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