Jerome Fine replies: The only time I did this, it just worked. But then, I was using an actual RX23 from DEC. Plus, you MUST have an RQDX3 controller. An RQDX2 and an RQDX1 WILL NOT WORK with an RX33. Plus, if you want to WRITE to the floppy, you MUST (I have not tried anything else, but I have been strongly advised) use the HD 5 1/4" floppy disks. The hardware format is identical to that for the PC and the number if blocks is 2400 instead of only 800 for an RX50. If you are able to get the first RX33 working and you do not like the open aspect of the drive, I have seen a second RX33 drive mounted along with the first RX33 - both right side up - inside the shell of the RX50 dual that you have which does not work very well. This solves the problem of protecting an open drive. I do have 3 spare RX50s which I could trade. I had been keeping them for a while and now that much of the PDP-11 software can be run on a PC, the RX50s are no longer as important. If you still want to use the RX50 media, you can FORMAT them (MAKE SURE THEY ARE DSDD floppy diskettes) on the PC using a program called PUTR (written by John Wilson): http://www.dbit.com/pub/putr/ On the PC, you MUST use a HD 1.2 MByte floppy drive. You can also read and write both RX50 and RX33 floppy diskettes on the PC with an RT-11 file structure. Sincerely yours, Jerome Fine RT-11/TSX-PLUS User/Addict Year 2000 Solutions for Legacy RT-11 Applications (Sources not always required)