TSS/8 on RK05

[Josh Dersch]

Hi all --

We've wanted to run TSS/8 on one of our PDP-8 systems at LCM+L for a long
time now, and while we contemplated either (a) restoring our RF08 or (b)
building an RF08 emulator, I decided it might be fun to investigate a third
option: (c) modify TSS/8 to run off hardware we already have running,
namely an RK05 drive.

And it /was/ fun!  And seems to have been successful, as we now have TSS/8
running on our PDP-8/e.  Performance is acceptable, and it seems to be
stable so far.  The changes I made are here:

https://github.com/livingcomputermuseum/cpus-pdp8

This is a fork of a codebase that Brad Parker put together a number of
years back in which he did some serious work to get TSS/8 to build (amongst
other things).  I made use of this effort, which saved a lot of time and
made building/testing my changes quite straightforward.

I also modified the disk image:  It's extended to 1MW (the maximum possible
without modifying the filesystem code) and I ported a couple of extra
programs to TSS/8 (CHEKMO and LISP).

I figured some people here might also be able to take advantage of being
able to run TSS/8 from RK05.  I know RK8E's are pretty rare, but I'm also
guessing more people have them than have working fixed-head disks :).  If
you do give it a try, let me know if you run into any issues or if you have
any feature requests.

Thanks,
Josh