PDP-11 DRV11-B question

That's almost certainly what's wrong. The software probably checks for the presence of a device at the address(es) it expects for the ADV11; that's very easy to do (just set up a trap handler in case it causes a bus timeout, then try to read from the address. If it doesn't cause a trap, the device is there.) The standard adresses for an ADV11 are 170400 for the CSR and 170402 for the Data Buffer Register. The standard addresses for a DRV11 are 167770 for CSR, and 167772 and 167774 for the OUTBUF and INBUF registers. If you haven't got an ADV11, I can think of three options open to you: 1) get an ADV11 2) get a 3rd party equivalent, such as an ADAC card 3) use some other device, set it to the ADV11 addresses, and hope you fool the software -- Pete Peter Turnbull Network Manager University of York