[TUHS] v6 archaeology continued - dds?

[Will Senn via TUHS]

Hi All,

After getting graphics and speech working, I turned to games and seeing 
what graphics were in play with the distribution beyond character 
graphics. Seems like Spacewar! worked on PDP1, surely some the 
distributed games would do graphics. Well, I pulled up pristine v6 and 
looked for game source - nowhere to be found of course, until that is, 
the excavation of the DMR tapes, where most of the games have a version 
of source as close to original as could be desired. Sadly, not graphics, 
per se.

Unfortunately, I wasn't able to find source for cubic, so I turned to ai 
for a insight and had it disassemble the code and found that in addition 
to the text output that it was also optionally opening /dev/ttyc and 
exec'ing /usr/bin/dds. These are interfaces to a picturephone, as 
mentioned in the Ritchie, Thomposon article:

There are also several one-of-a-kind devices including a Picturephone® 
interface, a voice response unit, a voice synthesizer, a 
phototypesetter, a digital switching network, and a satellite PDP-11/20 
which generates vectors, curves, and characters on a Tektronix 611 
storage-tube display.

Wanna see one (scroll down to pg. 141):

https://www.telephonecollectors.info/index.php/browse/document-repository/catalogs-manuals/bell-system-we/pubs-docs/blr/11616-69jun-blr-p138-picturephone/file

Apparently, by V3, this was has been tech (from ddsput(3)):
These routines *used* to provide an interface to the Display Data Set, a 
peculiar device which can be called by Picturephone sets and which will 
display some of the ASCII character set and certain other graphics on 
the Picturephone screen.

DDSPUT and DDSINIT are the referenced routines.

Anyhow, it was disappointing to find that it wasn't putting any graphics 
to the picturephone, just a text representation. However, it did print 
the full full 4x4x4 board to the display, vs the paltry 3 digits we get 
in the terminal, something along the lines of:

   1111 2222 3333 4444
   1234 1234 1234 1234

1 --x- ---- ---- ----
2 ---- -o-- ---- ----
3 ---- ---- x--- --x-
4 ---- ---- ---- o---

vs

113
222
331
433
441

The digits correspond to plane, row, column:
* first digit = which 4×4 plane/block (1–4)
* second digit = displayed row (1–4)
* third digit = position within that block (1–4)

My current thinking is to get cubic working again by taking essentially 
the same approach I used for the V6 speech and graphics work: preserve 
the old UNIX-facing interface and replace the vanished hardware beyond 
it. Rather than trying to reproduce an actual Picturephone DDS, I would 
recreate the /usr/bin/dds -> /dev/ttyc path and translate the DDS 
character/cursor operations onto the same SIMH display machinery I am 
already using for the vt work. That would put cubic back on a persistent 
graphical display, using the same general graphics path that is already 
supporting BASIC and FORTRAN through the V6 vt implementation.

What I would ask of y'all is - do you remember the display, have source, 
know provenance, have interesting story, etc?

Regards,

Will