You'll probably want to get in touch with TyRaNiD. He had written up some notes on programming the CD interface. He sent them to me a while ago, but I think I lost them in an HD crash. I'll also check my own doc collection to see if I can find anything, but that probably only has SGL/BIOS info, and maybe some architectural notes on the capabilities of the reader. There should also be a thread lurking around somewhere in this board that describes how to trigger the security signature check, which could provide some valuable clues for BIOS/SGL reverse engineering, if it comes to that.