> Does RX device on the PDP-11 use track 0 ? No, none of the DEC PDP-11 operating systems used track 0 on 8" floppies, as far as I can tell. > Does RX floppy use skew factor ? Yes, but I cannot remember what it is right now. Those darn brain cells just aren't as reliable as they once were. :-) When you get to the RX50, it is even more bizzare! Alan