Standalone floppy copy for PDT-11/150

 A goodly while back, I saved some PDT-11/150s from the dumpster. These are interesting little boxes. They contain a sort-of PDP-11/03 CPU, some memory, some terminal lines, and two RX floppy drives. Of note is their busless construction - instead of a Qbus and plug in memory and controller cards, the interface for the devices is provided by an 8085 microprocessor located on the CPU board. Also unique (as far as I know) is the size of the IO page - instead of 8KB like on all other PDP11s, this one has a 4KB IO page (I'm guessing, they did that to make 4KB more available to user programs).

  I've always thought that if DEC had marketed these for hobby and home use we could have prevented the rise of the PC and X86, but...that's not how it turned out on this timeline.

  Anyway, when I got them they didn't have any software. I managed to find an RT11 floppy that was purported to run on it. I was reluctant to use that floppy, though, since it was old even back then, and I didn't want to risk my only diskette with software on it without making a backup first.

  A look at the Users Guide for the PDT-11/150 showed that it would be pretty simple to write a program that I could "toggle in" with ODT that would copy a floppy.  I wrote DXCOPY to do just that, and it enabled me to copy the original RT disk to some working diskettes that I could then use without fear of losing the original. After I got RT-11 installed, and figured out how to work it, then I was able to use it to make copies instead. 

  On the remote chance that anyone out there besides me has any interest in working on a PDT-11/150 at this late a date, I include DXCOPY here. The values to load are included in the comment field - just load them with ODT at some address above 2000, load a source floppy in drive 0 and a destination floppy in drive 1, and give it the G command. When it finishes the hellishly loud thrashing of its heads back and forth, and the copy is complete, it will HALT. No user interface, no error checking or messages - just the bits flying from one disk to the other.

dxcopy.mac