I have a few instruments all connected to one GPIB, 488.2 bus controlled by one computer, Windows 10, updated, etc. One of the instruments is another computer with a PCIe-GPIB card. That computer does plenty of work, but the data transfer between the two is minimal and one way, just a few short commands. The data transfer is managed by proprietary software that came with the system, so when it's all working, the short commands cause it to do things.
While this usually works, intermittently it doesn't. NI Max on each computer sees all the instruments on the bus except the other computer, simultaneously. If I disconnect everything else, and run the cable from one computer to the other, neither see any instruments. The software, then, would seem to be irrelevant. I've restarted both systems, reset, refreshed, scanned, and knocked my head against the concrete. It seems these two instruments just don't want to talk to each other! What have I missed?
computer 1 (desired system controller): GPIB interface ID GPIB0, primary address 0, System Controller true, enable autopolling true. USB-GPIB interface, v18.5.0f0
computer 2 (desired slave): GPIB interface ID GPIB1 (or GPIB0), primary address 1, system controller false, enable autopolling false. Windows 7, PCIe-GPIB, v18.5.0f0.