Hello,
I'm interested in a free software BIOS for the newer Radeon cards which use the AtomBIOS format. The previous legacy BIOS is completely x86 assembly code unique to each card, but the AtomBIOS is modular and *should* be easier to replace. I haven't really done any serious work on this yet, and it's just a spare time project (which isn't very much because of other projects and real life) but there seems to be some interest.
There is some information on my blog (http://olivermcfadden.livejournal.com/) trying to figure out how to flash these cards, but I think it's some kind of GPIO based SPI interface.
AMD have released some register information for the Radeon cards (http://www.x.org/docs/AMD/42589_rv630_rrg_1.01o.pdf and http://www.x.org/docs/AMD/RRG-216M56-03oOEM.pdf) and a working AtomBIOS parser in the radeonhd driver (http://gitweb.freedesktop.org/?p=xorg/driver/xf86-video-radeonhd;a=summary)
I believe the parser in radeonhd is also compiled into the BIOS flashed to the card. I guessed this from some left over preprocessor defines, etc.
As far as I know, the AtomBIOS on the card consists of an interpreter in x86 code, some binary scripts executed by the interpreter, and some data tables, all wrapped up inside the PCI expansion ROM format.
The opcodes and format of the binary scripts and data tables are described by the parser code, so I think there is enough information, except for how to actually flash the on-card ROM...
I don't whether there is much interest for this project, but at least one LinuxBIOS developer seems interested, so let's see where it goes...