Hi It is also an early system. Most newer systems don't come with the Digital Systems drives. This is one of the rarer DMA type setups with the controller made from TTL. I would love to get a copy of the Digital Systems manual. I'll be watching this one to see who wins it. Maybe they won't mind making a copy of the manual for me. When I got my IMSAI, it had this drive system. I had to figure out the floppy controller by figuring out the PROMs used in the state machine. I wrote my own BIOS for it as well. It was a lot of work. It wasn't until a few years later that I found someone else with one of these controllers and actually got an original BIOS. It was almost identical with mine ( no big surprise ). I still use my IMSAI because it is handy to do my 8080 assembly on ( and more fun ). Dwight