[COFF] Re: [TUHS] Re: Origins of the frame buffer device

[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: 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: 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.