Steve Jones wrote: I should hedge my bets here: There is no Qbus backplane in the PDT-11/150. There are some stacking connectors between two dual- height sized boards (serial ports and memory) on top and the middle board, which carries the CPU complex. I believe the bottom board in the stack is the floppy controller - not sure if the console circuitry (8085 based?) is on that or the middle board. Now, where on earth do I have the docs for that critter... --Steve. smj(at)spamfree.crash.com (lose spamfree to get through, m'kay?)