So I figured I should start a log of what's been going on here. I've thought about starting a web page about all this, but I'm not entirely sure about that yet.
So far, I have a working disassembler, a lot of research on the TI, and I am starting on a port of GCC to the TMS9900 processor. The disassembler is written in perl, and doesn't know about the object format. It just converts a byte stream into assembly. It is up to the user to figure out what is code and what is data.
The plan right now is to use the ELF object format instead of the DX80 format from TI. This is mostly due to the number of tools which can work with the ELF format. After a while I will probably make a DX80 format for GCC.
I'm torn on the object format choice. Mainly because I don't want to throw away all the old TI stuff. Unfortunately, the old software will assume it has all hardware resources at its disposal, and I won't have any way to contain it.
I've recently got the GAS port to assemble Type I instructions (simple ALU instructions), as long as they do not use constants.