I don't know about the software run on the two PDP-6's - by the time I arrived at MIT, they were both powered off and never, as far as I know, ever ran again. I would _assume_ that it ran ITS. I don't recall if the physical remains stayed until the KA's were de-commissioned, or of they were removed prior to that - I suspect they stayed, since they were mixed in with the KA's - in the case of AI at least, wired in together - but don't remember exactly. I don't recall if the I/O bus was shared between the two CPUs on the DM machines, the way it was on the AI KA and PDP-6. The DM PDP-6 was part of the DM KA 'assembly' - DM was in two rows (front and back) to the right of the right-hand door from the lobby into the machine room. IIRC, the PDP-6 was in the front row, to the right? of the KA CPU. (The back row contained memory boxes - a mix of different DEC memories. I don't recall where the tape and disk controllers were - or the disk drives. I seem to vaguely recall a few boxes to the left of the KA CPU? Maybe there are some pictures of the MAC machine room that will show it.) Noel