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PostPosted: Wed Oct 28, 2015 12:56 pm 
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I'm just wondering if there is any documentation on rewriting games for the Nintendo Entertainment System to the Game Boy Color. I got time and I fan game I want to work on that I would like the better hardware of the Game Boy Color to work with, but I would like to keep a similar game play to the original; I just wanted to make a sort of fan sequel with some additional features. Also on a side note I know that some Game Boy Color games were backwards compatible with the original game boy, is there any documentation on that?


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PostPosted: Wed Oct 28, 2015 2:29 pm 
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GBC games have a "uses GBC features" byte in their header. When run on a GBC, the BIOS detects this byte, sets up the video hardware slightly differently, and passes an identifying value to the game in (I think) CPU registers.

Dual-mode (black cartridge) games use this register value to determine whether to enable GBC-specific engine features. Some games may run at a higher frame rate on a GBC using these features:
  • Double speed processing
  • CHR HDMA (as opposed to slower PIO copying)
  • Faster LCD (as opposed to blur)
Some may show more graphic detail using these features:
  • Double CHR RAM
  • GBC palettes
  • Tile attributes (color, flipping, and an extra bit of tile number)
Some may lock out parts of the game that can't be squeezed into the older hardware:
  • Paged work RAM
  • Color-specific bonus levels (the color dungeon in Link's Awakening DX and most of Conker's Pocket Tales)

Later in the GBC's life, games became so dependent on these features, especially CHR HDMA, double CHR RAM, double speed, and paged work RAM, that they didn't bother to even try to advance past the legal notice screen on monochrome systems at all. These came in clear cartridges.


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PostPosted: Wed Oct 28, 2015 2:36 pm 
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Can you be specific about what sort of "documentation" you're looking for? The NES and GBC are similar in power but otherwise very different systems. Rewriting a game for the GBC basically constitutes...rewriting the game.


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PostPosted: Wed Oct 28, 2015 4:14 pm 
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adam_smasher wrote:
Can you be specific about what sort of "documentation" you're looking for? The NES and GBC are similar in power but otherwise very different systems. Rewriting a game for the GBC basically constitutes...rewriting the game.

Okay so if I understand correctly it there isn't any special tricks or shortcuts you can take specific to this.


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PostPosted: Wed Oct 28, 2015 4:28 pm 
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At the turn of the millennium, I remember reading an "official" Nintendo PDF that explained how to convert NES games to GBC games, keeping some of the limitations in mind. So, search for that.

However with Google, just as with people, your queries will need to be more specific than they are right now.

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PostPosted: Wed Oct 28, 2015 5:17 pm 
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ccovell wrote:
At the turn of the millennium, I remember reading an "official" Nintendo PDF that explained how to convert NES games to GBC games, keeping some of the limitations in mind. So, search for that.

However with Google, just as with people, your queries will need to be more specific than they are right now.

This wouldn't happen to be it would it?
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=14&cad=rja&uact=8&ved=0CHgQFjANahUKEwj-qKWds-bIAhVFMyYKHViuBls&url=http%3A%2F%2Fwww.start-game.com%2Ffiles%2Fgbcprimer.doc&usg=AFQjCNE6dEWRDl96Lj2Ezqfw0qgmCtR8XQ&sig2=6cUnr_4lW1rX6QXgfMwwbg


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PostPosted: Wed Oct 28, 2015 6:21 pm 
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And in case "gbcprimer" gets taken down, substantially all of the information therein about the GBC's capability appeared in Nintendo Power magazines preceding the GBC's launch.


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PostPosted: Thu Oct 29, 2015 10:58 am 
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tepples wrote:
And in case "gbcprimer" gets taken down, substantially all of the information therein about the GBC's capability appeared in Nintendo Power magazines preceding the GBC's launch.

There used to be a site too. Just had this exact same info. My guess is they just copied the site or the other way the site was copied. The site been offline for years now, found it on archive.org. This site http://www.devrs.com/gb/ still links to the original site which is way I looked it up on the archive (said info about converting NES games to GBC). My guess is GBCPrimer wasn't official (the site's home page looked worse the ctcd at around the same time), probably just got the info from Nintendo Power or something.


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