a little more history about the XGPs of the 70's...

On Fri, Jul 31, 2020 at 10:16 AM Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:
    Or maybe it was an -11/20 early, and then it got replaced with an -11/10? (I
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 ;-)