Can disks be copied using only one RL02 drive?

[Ethan Dicks]

On 5/3/07, charlesmorris at hughes.net <charlesmorris at hughes.net> wrote:
> I've got a PDP-11/23+ with 4 Mb RAM, but only one RL02 and no software
> except an XXDP pack. Henk Gooijen helpfully made for me a (RT-11)
> bootable pack that is on the way (if the post offices between Europe
> and the US don't lose or destroy it). So I definitely want to make a
> backup copy.

Sure.

> Is this possible to do with only one drive? Apparently you can't swap
> disks back and forth like the old DOS or CP/M systems.

There certainly is no in-built facility to RT-11 to do a
single-disk-swap as there was with many 8-bit micros.  I suppose you
could write a utility to do a disk copy in 3 swaps, but I am unaware
of any such program.

> Henk thinks
> creating a RAM disk would work, and copy files but I don't know
> anything about RT-11.

That might work, but I don't think you can use RT-11 to write the
system area when fiddling packs like that.  If you had a different
boot medium, floppy, say, you could treat the RL02 drive as a data
volume, then it wouldn't matter.  The RL02 just becomes another drive
at that point.

> The alternative is to take the RL02 from my PDP-8/A and connect it,
> but then I don't have a "1" key, they are both unit "0".

That should be easier to remedy than just about anything else.  If you
can get a '1' (or '2' or '3') or even a third '0' and modify it, that
should work.  Alternately, there's probably a way to override the
switches from behind, or just unplug the switch board and construct
and attach a functional replica that doesn't depend on pre-molded
plugs.

Another approach would be to pipe the contents of your RT-11 pack to
the PC as a backup.  VTserver should be able to do this for you.
Below is a pointer to the 'readme'.  Pay attention to the part about
treading lightly around the last cylinder.  It can cause problems to
overwrite the bad block area.

http://www.tuhs.org/Archive/PDP-11/Tools/Tapes/Vtserver/
http://www.tuhs.org/Archive/PDP-11/Tools/Tapes/Vtserver/vtreadme.html

I haven't used vtserver in a long time, but I'm sure there are folks
on the list who can share their experiences.

-ethan