You must be talking of the PDT-11/150 then. The /110 and /130 sat inside a VT100 shell. Extremely similar to a VT103 (I actually never figured out what the difference between a VT103 and a PDT-11/130 is.) I may be grossly misinformed, but my understanding is that although the /110 and /130 both live inside a VT100, they're *not* like VT103s, and have no Q-bus but use a custom CPU board just like the /150 (I doubt it's the exact same board, but a similar design). I could have sworn the 110/130 manual on bitsavers (which is misfiled away from the 150 manual -- I forget where) said so but on a quick skim I can't find it. The I/O hardware has enough programming differences that it can't be regular Q-bus stuff, although I suppose they could have made a whole set of PDT-specific boards. Yes, I think that's the case. I found a paragraph in the PDT 11/130 manual that states that the PDT family all have "bounded bus" systems that are completely buried in the PDT card, and an 8 bit processor actually talks to the IO devices. It also says that a word transfer to the IO system takes 90 microseconds, and a byte transfer takes 180 seconds, so that explains the logic behind the optimization. I never thought of any of them running any type of RSX - I ll have to dust off one of my PDT-11/150s and see if I can get some sort o' RSX on it. -- Lee K. Gleason N5ZMR Control-G Consultants lee.gleason at comcast.net