Gameboy Circuit Diagram, GB development wiki/forum and som breaking news

September 20th, 2008

I’m writing this post because every once in a while, people end up here when googling for thing like “Gameboy circuit” or “Gameboy schematic”. This is why this post is placed in the category circuit bending, so that people will find it.
If you googled for that, here’s probably what you’re looking for:
Gameboy DMG schematics
SuperGameboy SGB schematics

A word about that wiki linked above. It’s a Gameboy development wiki that I’m hosting together with a Gameboy development forum. It’s a narrow subject, and the forum it’s typically low traffic. But if you do have questions about Gameboy software development, feel free to drop by the forums and ask.

In other news:
1) The GBC bootstrap is about to be dumped. What is the GBC bootstrap, you may wonder… (If you’re not into low level software development, you’ll likely not understand the following) The bootstrap is the vey first piece of code that runs on any (Z80 type) Gameboy when it boots up. It checks that the header checksumsare correct and displays the Nintendo logo. This tiny piece of code is only 256 bytes big. For you GB developers out there, the bootstrap is the reason why the entry point is $100 and not $0. The reason why this piece of code is interesting is of pure curiosity, and because it’s the last undocumented secret of the Gameboy.
5 years ago, Neviksti managed to dump the bootstrap from the DMG. (The original Gameboy) Read about it here. The news I have today is that the corresponding bootstrap ROM for the GBC is about to be dumped. And in fact it’s not just a 256 byte area located at $0-$FF but to other memory areas sized 512 bytes and 1792 ($700) bytes. These are believed to be storage for the the big “Gameboy” logo shown on CGB’s during bootup and palettes for colorizing monochrome games.
At this point I can’t tell you who’s working on dumping the bootstrap ROMs (At that person’s request) but hopefully I will be able to distribute the contents of the bootstrap ROMs when they have been dumped.
2) The other breaking news is that dwedit and Palmertech, have, at least partially succeeded in booting GBC games on a GB micro by doing a special software trick. At the very least they’ve managed to enter GBC mode. I’m not sure whether they succeeded in actually running GB code after the mode switch, but they’ve managed to make it run the GBC bootstrap. (In principle the same bootstrap as mentioned above) I’ve tried the hack too, ona GBA 1st gen and a GBA SP, and both showed a black screen but played the startup sound. But I’m trying to contact dwedit for more info, and I’ll try to do my own research on the subject, so expect to hear more about it.
For now, check this thread on pH if you’re interested:

2 Responses to “Gameboy Circuit Diagram, GB development wiki/forum and som breaking news”

  1. James Lee S. Tabao II says:

    gameboy sp can be use to as tv

  2. James Lee S. Tabao II says:

    gba sp can be use for tv tunning

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