* [COFF] Re: [TUHS] Re: Origins of the frame buffer device
[not found] ` <7w7cvr4x36.fsf@junk.nocrew.org>
@ 2023-03-29 23:07 ` Rob Gingell
0 siblings, 0 replies; 2+ messages in thread
From: Rob Gingell @ 2023-03-29 23:07 UTC (permalink / raw)
To: Lars Brinkhoff, Noel Chiappa, Larry McVoy, segaloco; +Cc: Paul Ruizendaal, coff
[Redirected to COFF for some anecdotal E&S-related history and non-UNIX
terminal room nostalgia.]
On 3/7/23 9:43 PM, Lars Brinkhoff wrote:
> Noel Chiappa wrote:
>>> The first frame buffers from Evans and Sutherland were at University
>>> of Utah, DOD SITES and NYIT CGL as I recall. Circa 1974 to 1978.
>>
>> Were those on PDP-11's, or PDP-10's? (Really early E+S gear attached to
>> PDP-10's; '74-'78 sounds like an interim period.)
>
> The Picture System from 1974 was based on a PDP-11/05. It looks like
> vector graphics rather than a frame buffer though.
>
> http://archive.computerhistory.org/resources/text/Evans_Sutherland/EvansSutherland.3D.1974.102646288.pdf
E&S LDS-1s used PDP-10s as their host systems. LDS-2s could at least in
principle use several different hosts (including spanning a range of
word sizes, e.g., a SEL-840 with 24 bit words or a 16 bit PDP-11.)
The Line Drawing Systems drove calligraphic displays. No frame buffers.
The early Picture Systems (like the brochure referenced by Lars) also
drove calligraphic displays but did sport a line segment "refresh
buffer" so that screen refreshes weren't dependent on the whole
pipeline's performance.
At least one heavily customized LDS-2 (described further below) produced
raster output by 1974 (and likely earlier in design and testing) and had
a buffer for raster refresh which exhibited some of what we think of as
the functionality of a frame buffer fitting the time frame referenced by
Noel for other E&S products.
On 3/8/23 10:21 AM, Larry McVoy wrote:
> I really miss terminal rooms. I learned so much looking over the
> shoulders of more experienced people.
Completely agree. They were the "playground learning" that did all of
educate, build craft and community, and occasionally bestow humility.
Although it completely predates frame buffer technology, the PDP-10
terminal room of the research computing environment at CWRU in the 1970s
was especially remarkable as well as personally influential. All
(calligraphic) graphics terminals and displays (though later a few
Datapoint CRTs appeared.) There was an LDS-1 hosted on the PDP-10 and
later an LDS-2 (which was co-located but not part of the PDP-10
environment.)
The chair of the department, Edward (Ted) Glaser, had been recruited
from MIT in 1968 and was heavily influential in guiding the graphics
orientation of the facilities, and later, in the design of the
customized LDS-2. Especially remarkable as he had been blind since he
was 8. He had a comprehensive vision of systems and thinking about them
that influenced a lot about the department's programs and research.
When I arrived in 1972, I only had a fleeting overlap with the LDS-1 to
experience some of its games (color wheel lorgnettes and carrier
landings!). The PDP-10 was being modified for TENEX and the LDS-1 was
being decommissioned. I recall a tablet and button box for LDS-1 input
devices.
The room was kept dimly lit with the overhead lighting off and only the
glow of the displays and small wattage desk lamps. It shared the raised
floor environment with the PDP-10 machine room (though was walled off
from it) and so had a "quiet-loud" aura from all the white noise. The
white noise cocooned you but permitted conversation and interaction with
others that didn't usually disturb the uninvolved.
The luxury terminals were IMLAC PDS-1s. There was a detachable switch
and indicator console that could be swapped between them for debugging
or if you simply liked having the blinking lights in view. When not in
use for real work the IMLACs would run Space War, much to the detriment
of IMLAC keyboards. They could handle pretty complex displays, like, a
screen full of dense text before flicker might set in. Light pens
provided pointing input.
The bulk of the terminals were an array of DEC VT02s. Storage tube
displays (so no animation possible), but with joysticks for pointing and
interacting. There were never many VT02s made and we always believed we
had the largest single collection of them.
None of these had character generators. The LDS-1 and the IMLACs drew
their own characters programmatically. A PDP-8/I drove the VT02s and
stroked all the characters. It did it at about 2400 baud but when the 8
got busy you could perceive the drawing of the characters like a scribe
on speed. If you stood way back to take in the room you could also watch
the PDP-8 going around as the screens brightened momentarily as the
characters/images were drawn. I was told that CWRU wrote the software
for the PDP-8 and gave it to DEC, in return DEC gave CWRU $1 and the
biggest line printer they sold. (The line printer did upper and lower
case, and the University archivists swooned when presented with theses
printed on it -- RUNOFF being akin to magic in a typewriter primitive
world.)
Until the Datapoint terminals arrived all the devices in the room either
were computers themselves or front-ended by one. Although I only saw it
happen once, the LDS-1 with it's rather intimate connection to the -10
was particularly attuned to the status of TOPS-10 and would flash
"CRASH" before users could tell that something was wrong vs. just being
slow.
(We would later run TOPS-10 for amusement. The system had 128K words in
total: 4 MA10 16K bays and 1 MD10 64K bay. TENEX needed a minimum of 80K
to "operate" though it'd be misleading to describe that configuration as
"running". If we lost the MD10 bay that meant no TENEX so we had a
DECtape-swapping configuration of TOPS-10 for such moments because,
well, a PDP-10 with 8 DECtapes twirling is pretty humorously theatrical.)
All the displays (even the later Datapoints) had green or blue-green
phosphors. This had the side effect that after several hours of
staring at them made anything which was white look pink. This was
especially pronounced in the winter in that being Cleveland it wasn't
that unusual to leave to find a large deposit of seemingly psychedelic
snow that hadn't been there when you went in.
The LDS-2 arrived in the winter of 1973-4. It was a highly modified
LDS-2 that produced raster graphics and shaded images in real-time. It
was the first system to do that and was called the Case Shaded Graphics
System (SGS). (E&S called it the Halftone System as it wouldn't do color
in real-time. In addition to a black & white raster display, It had a
35mm movie camera, a Polaroid camera, and an RGB filter that would
triple-expose each frame and so in a small way retained the charm of the
lorgnettes used on the LDS-1 to make color happen but not in real-time.)
It was hosted by a PDP-11/40 running RT-11.
Declining memory prices helped enable the innovations in the SGS as it
incorporated more memory components than the previous calligraphic
systems. The graphics pipeline was extended such that after translation
and clipping there was a Y-sort box that ordered the polygons from top
to bottom for raster scanning followed by a Visible Surface Processor
that separated hither from yon and finally a Gouraud Shader that
produced the final image to a monitor or one of the cameras. Physically
the system was 5 or maybe 6 bays long not including the 11/40 bay.
The SGS had some teething problems after its delivery. Ivan Sutherland
even came to Cleveland to work on it though he has claimed his main
memory of that is the gunfire he heard from the Howard Johnson's hotel
next to campus. The University was encircled by several distressed
communities at the time. A "bullet hole through glass" decal appeared on
the window of the SGS's camera bay to commemorate his experience.
The SGS configuration was unique but a number of its elements were
incorporated into later Picture Systems. It's my impression that the LDS
systems were pretty "one off" and the Picture Systems became the
(relative) "volume, off the shelf" product from E&S. (I'd love to read a
history of all the things E&S did in that era.)
By 1975-6 the SGS was being used by projects ranging from SST stress
analyses to mathematicians producing videos of theoretical concepts. The
exaggerated images of stresses on aircraft structures got pretty widely
distributed and referenced at the time. The SGS was more of a production
system used by other departments and entities rather than computer
graphics research as such, in some ways its (engineering) research
utility was achieved by its having existed. One student, Ben Jones,
created an extended ALGOL-60 to allow programming in something other
than the assembly language.
As the SGS came online in 1975 the PDP-10 was being decommissioned and
the calligraphic technologies associated with it vanished along with it.
A couple of years later a couple of Teraks appeared and by the end of
the 1970s frame buffers as we generally think of them were economically
practical. That along with other processing improvements rendered the
SGS obsolete and and so it was decommissioned in 1980 and donated to the
Computer History Museum where I imagine it sits in storage next to a
LINC-8 or the Ark of the Covenant or something.
One of the SGS's bays (containing the LDS-2 Channel Control, the front
of the pipeline LDS program interpreter running out of the host's
memory) and the PDP-11 interface is visible via this link:
https://www.computerhistory.org/collections/catalog/102691213
The bezels on the E&S bays were cosmetically like the DEC ones of the
same era. They were all smoked glass so the blinking lights were visible
but had to be raised if you wanted to see the identifying legends for them.
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