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Building Consoles For Fun
tierra writes "Indiviuals writing their own games is one thing, but try building your own console. Russ Christensen, and his team put together in class, dive into the fun of using an old Nintendo system to house their customized XSA-50 Board. They also uses a XSA Extender to hook their personal console up to a monitor instead of a TV. They programmed Tetris and Space Invaders for their console using a system they call CASM."
1) Unified memory architecture.
2) Close to Win32, but not quite.
3) Liberal use of hashing and checksumming.
The XBE executable format is actually pretty interesting - it's similar to Win32's PE, but with many more flags and tables - for example, bitfields for what mediums are acceptable to run the game off of (DVD, hard drive, CD-RW, etc.) Each section and the relocation address tables have a SHA-1 hash taken of it, the header containing the section offsets and hashes of each is itself hashed, digitally signed using PKE, and then encrypted.
The hard drive also uses the ATA spec's password protection, although that's already been bypassed and the drive dumped. In any case, most people with homebrew code are using the neXgen or EvoX dashboards to run an FTP server on the XBox for uploading and downloading files to the HDD, so you don't have to muck about with IDE cables.
Most of the modchips out there right now work by tying the chip enable pin on the on-board BIOS to to ground, and emulating the BIOS directly on the LPC bus to allow execution of unsigned code and ignore mismatched media flags. (BTW, kudos to MSFT for complicating things with a floating ground... more than a few early modchips were responsible for fried PCs while doing in-circuit programming.)
I love projects like this. May just the fact that they succeeded inspire others to try the same thing.
On a tangent, this is the kind of thing that's been very possible for some time, but most people blindly assume that it's much too difficult. Similarly, writing a compiler for a high level language is a relatively easy project. You could do it in a semester course, or a month of spare time, but mention "writing a compiler" to the great majority of programmers, even those with lots of experience, and they run away in terror.
Personal chip design reached critical mass back around 1994.