Thanks everybody for the clear replies. I removed the bus expansion card (for the external box) and when I powered up the system again, it just ran fine. The next step I did was move the RQXD3 to the location where that bus expansion card was and where the RQDX3 was I inserted a DELQA (M7516). I connected the bulkhead cable and mounted a 10Base2 transceiver on the AUI connector. The 10Base2 transceiver has the bare minimum network: just the T-connector with on both sides 50 Ohms terminators. The system still boots and runs fine, but I expected to see the XE: (?) device listed with the $SHOW DEVICES command. (The system runs Micro/RSX 3.1). Current config: slot 1 A/B-C/D : M7554-02 KDJ11, 15 MHz, 1.5 Mb slot 2 A/B : M3106 4 line EIA MUX slot 3 A/B : M7546 TQK50 slot 4 A/B : M7516 DELQA C/D : M7555 RQDX3 all other slots are empty. Must the system with the new DELQA interface be sys/generated? Am I doing something wrong? TIA - Henk.