27 Jan
2023
27 Jan
'23
6:58 p.m.
On Jan 27, 2023, at 11:23 AM, Jon Elson via cctalk
<cctalk(a)classiccmp.org> wrote:
On 1/26/23 19:13, Paul Koning via cctalk wrote:
Interesting. I maintained a bunch of Versatec 1200A
printers at work, and ended up with a couple of them at home. horrible paper, like a
dirty chalkboard, smelly toner, if the paper was handled before it dried the toner could
come off on your hands, etc. But, I had never seen the issue with gaps in graphics, and
our drivers, especially on the Nat Semi 16032 system was VERY slow in graphics mode.
Perhaps it was misalignment, or maybe a different model. I definitely remember the chain
drive, and the play it had, and the defective printout. The solution was to run in
"streaming mode" -- non-stop data. Hard to do given that the mainframe ran a
bunch of high priority real time jobs: the PLATO components. Solution: do the entire job
in a peripheral processor, using the CPU only to provide an I/O buffer area for reading
the file being printed.
I remember the funny paper, not so much the smelly toner. It wasn't as bad as the
screen capture printer we had one floor down, made (I think) by Varian -- it somehow
captured the image on the orange dot plasma panel display using strange paper and nasty
liquid toner. The process used is a mystery to me; it had to be some optical magic
because you can't, as far as I know, read out the state of a PLATO terminal plasma
panel electronically. Those panels are bistable, the pixels are actual memory cells, but
I can't think of a way to sense electrically whether one is on or off.
On Jan 26, 2023, at 6:29 PM, Chuck Guzis via
cctalk <cctalk(a)classiccmp.org> wrote:
I take that back about Versatec, CHM has a document from 1970 on their
electrostatic printer:
https://www.computerhistory.org/collections/catalog/X163.83A
I know that Lawrence Livermore had one and used it quite a bit back in
the day.
--Chuck
I worked with one of those on the PLATO system in 1976, where it was used
in bitmap graphics mode to print music scores. That at first worked very badly because
the paper transport was chain driven, with enough slack in the drive that if you'd
stop and start it, you'd get irregular paper feeding with as a result gaps in the
graphics. I fixed this by writing a new driver that was designed to stream, so it would
never stop in mid-job. When laser printers came out, I was VERRRY glad to
move into the future!
Jon
Definitely.
paul