Hello, may be someone of the readers could help solving my problem. A controller AT-GPIB/TNT (WinNT 4, Svp4) works correctly with some devices, same for an other PCI-GBIP (Win98). But connecting both "networks" hangs the bus, in spite of proper settings (controller/non-controller, EOI, ... as described in user manual, no conflicts on PC with IRQ,...). I've tried to vary communication parameters, to install original card drivers from manufacturer, ... - when both cards are connected to the same bus then nothing works properly, also the NI software doesn't correctly detect other devices during a scan in contrast to before. At the moment I don't know what to check, to try... any ideas are welcome. Thanks a lot.