RT-11 with dual MSCP controllers

While you have provided insufficient detail of which version of RT-11 you are using, along with a Mapped or UnMapped Monitor, I can guess a bit. For your information, I have FIVE MSCP controllers: DU(X).SYS - Standard CSR / VECTOR QR(X).SYS - RQDX3 (Q for a dual board) VR(X).SYS - RQDX2 (V for a quad board) SE(X),SYS - Dual ESDI controller for Seagate Hard Drives HI(X).SYS - Sigma RQD11-EC (Quad ESDI controller) for Hitachi Hard Drives I also have a CMD CQD220 / TM which is often used with the DU(X).SYS device driver for SCSI interface drives. If you "merely" made a copy of DU(X).SYS to SC(X).SYS, then critical values were not modified. In addition, if you SYSGENed an extended device driver which supports more than EIGHT physical units, there is one additional word which requires alteration. Unfortunately, DEC neglected to provide the command: SET SC NAME which would fix all of those other values when the NAME of the device driver is changed to support a second controller at a different CSR / VECTOR pair. But then, even though RT-11 is VERY comprehensive for a VERY simple operating system, there are still many enhancements that were omitted. If you are using an UnMapped Monitor (RT11FB) with ONLY a maximum of EIGHT physical units, then search for (use SIPP) the value ^rDU (16110) and change it to ^rSC (73470 - or whatever you have named your CQD220A/TM device driver). If you are using a Mapped Monitor, the names are a bit different. That will be in addition to: SET SC CSR=160334 SET SC VECTOR=150 (did you forget to change the VECTOR?) As far as I understand, you may be able to get by with just the above two SET commands without changing the ^rDU values if you just use the RQDX3 controller for the RX33 floppy as a data device. Please let me know what you find that fixes the problem or if you need more help. Jerome Fine