a little more history about the XGPs of the 70's...
On Fri, Jul 31, 2020 at 10:16 AM Noel Chiappa <jnc(a)mercury.lcs.mit.edu>
Or maybe it was an -11/20 early, and then it got
replaced with an
have a _very_ vague memory that the XGP's -11 was a /20, bur I wouldn't put
much weight on that.)
I was not involved when it was stood up, but FWIW the CMU mods to a Xerox
'Long Distance Xerography - LDX' (FAX) system was definitely was an 11/20
on the original one. The XGP as it was called, was the first Xeroxgraphic
printer at 200 dpi attached as an 'output device' to the PDP-11/20. A couple
of my friends and I did some of the programming of the graphics PDP-11 at
one point (you may remember the LDX used rolls of paper, with a razor to
cut when the page was complete. The PDP 11 was hacked it to recognize Mike
Shamos's PPN and cut his paper every 1.5 inches, giving him strips of
output, but work fine if the same job was printed by anyone else - story
for another day as to why). BTW, an interesting factoid about the LDX, is
that it was not a laser printer. It used a CRT, the same idea Tektronix
would use shortly thereafter for their hardcopy printers.
Anyway, I'm pretty sure the copies at Stanford (Jan '73), and MIT (was the
3rd in the series and a little later) also used 11/20s or maybe 11/15's
which was the OEM version of the 20 as it was March '72 when the CMU XGP
was first stood up. PARC made one too for MAXC shortly after that but I
think that had a Nova in it originally. That said, Jim Teter
might remember but I think that only a handful of them was them
stood up, but most used Jim's interface/mod. I think DEC one, as at least
the PDP-16/RTM handbook, was set using it/maybe a few others. I also am
under the impression that after the original wire-wrapped prototype worked,
the DR-11C to Xerox machine driver logic was an early numbered 'Teter Toy"
( My memory is the designers went to PC board quickly because the WW board
would not let them close the LDX cabinet or a shelf or something like that
). I also have memories of soldering/assembling some sort interface board
for XGP in the summer of '78 under the watchful eye of Teter which we were
assembling for some reason (a bunch of us were working as systems
operators/programmers and tech's -- *i.e.* grunt work).
I do have copies of the pictures of Teter printing CMU diploma replicas on
toilet paper with it in the late '70s.
Also, another fun XGP story, Chuck Geschke (Wulf’s first PhD student,
founder of Adobe) filed the first PhD printed on the XGP but the CMU
library would not accept it because they wanted the original ;-)