On Thu, Jun 15, 2023, 2:56 PM segaloco via COFF <coff(a)tuhs.org> wrote: Many terminal had a reverse video setting even in advance of the graphical interfaces Step forward to graphical systems and windows on the Alto? Light background You can add x10/x11 to the early list... as well as decwindows on the VAX station ii era... Fast forward to today, and it seems that dark themes are all the rage, Dark on light was to mimic paper. I'm also skeptical that light on dark uses less power or was easier to implement except maybe in the very earliest vector displays... Warner - Matt G.

On 6/15/23, segaloco via COFF <coff(a)tuhs.org> wrote: The phosphors on CRT screens don't last forever. You only want to light them when necessary. CRTs also suffer from the problem of burn-in. If you keep the same picture illuminated for a long period of time that pixel pattern gets burned into the phosphors. This is why the later GUI CRTs had screen saver software that displayed an ever-changing picture to prevent burn-in. This isn't a problem with the modern, non-cathode-ray displays. Good ol' flying toasters. -Paul W.

Matt, I take a small stab at this. Like most of us, I don't know the exact reason, but having lived the time, I'll point out a few things. 1.) At the start (60s and 70s), I suspect that economics drove light pixels on dark backgrounds as the high-order bit. 2.) Xerox PARC developed Alto was driven by their research in the Electronic Office -- remember Xerox made its money selling coping they tried to convince their management of the idea. 3.) High-resolution monitors were costly until the late 1980s (regardless of BW or Color) 4.) Early phosphors tubes suffered from burn, so turning on display "pixels" for long times was bad. That said, TV was constantly changing so it was less of an issue for them, but not for terminals where the dots were the same part of the screen over and over. 5.) "Glass Terminal" designed until the later 1970s were SSI/MSI TTL, with few if any VLSI except for maybe the WD1402A <https://streaklinks.com/BjB7EOaVlbWFCqrlggbSUziX/https%3A%2F%2Fspectrum.ieee.org%2Fchip-hall-of-fame-western-digital-wd1402a-uart> UART <https://streaklinks.com/BjB7EOa5ed7SuU43lgrt-Chq/https%3A%2F%2Fspectrum.ieee.org%2Fchip-hall-of-fame-western-digital-wd1402a-uart> 6.) Memory costs per bit compared to today are still high. Remember in 1980, when the CMU "SPICE" proposal came out for the infamous 3M system, we priced the cost of 1MByte of memory (only) which it needed (using Tektronix's volume pricing) at > $3K [BTW: this was the same year that Jake Grimes stood on a take at the Asilomar Microprocessor Workshop and declared memory as being "free" - and compared just a few years previous -- it was]. I observe a few things with those points as a place to start. If you look at the early "glass ttys" like the DEC VT05 and even later the LSI ADM3A - there is nary a microprocessor inside. It's a huge board with lots of TTL [the ADM 3A often came as a kit - you had to solder them yourself]. The other thing to remember, in those days, NTSC in the US and PAL in Europe for TVs was the primary driver for CRTs. So if you were making a display, you had to at least buy the tube from one of a small number of tube manufacturers [IIRC Phillps in the EU was the leader, and GE, RCA, and Raytheon fought it out in the US -- Sony would come later] - (I'm also not sure Magnovox made its own tubes). For instance, I believe DEC bought the tube for the VT05 from Raytheon; who made them locally ??Lowell, MA maybe?? and continued for a while [maybe even through the VT-100]. So remember, for a 25x80 terminal -- that's 2KBytes of memory just for the video [without "attributes"]. So that's also big. IIRC, the VT05, and ADM 3A used early Intel 1103 1Kx1 DRAM. So the eight memory chips are the highest cost part of the logic board. Because of the design, I suspect the turn-on-the-beam logic for a 'dot time" was all the designers cared about. Light on dark fell out of the ease of design, and they had limited BW on the tubes. Even with that, I believe the VT05 was in the $3-5K range in the late 1960s when it was sold for the PDP-8 or the like. I remember in the late 1970s when the $1K glass TTY (the cost of the ADM 3A kit) or the Pekin Elmer "Fox" terminals appeared. So between tubes and logic, it took at least ten years to drive the price down by a factor of 3-5. My friend and former cubical mate at Tektronix, Roger Bates designed the display in the Alto [side tidbit - he has the patent on the loadable curser - which was initially a martini glass, not an hourglass to show time]. Roger told me the monitor they used was a "special order" and was fairly expensive. But it was a definite choice to do black on white -- they wanted to represent paper. FWIW: a great deal of the monitor logic is done in microcode [the infamous BITBLT being an example] because they were already logic constrained. He and Thacker were using huge boards for the processor, and it was all SSI/MSI. *I think it's safe to suggest that Xerox was where the idea/first use of dark on light began.* FWIW, in 1979/80, when he and I were working on Magnolia at Tektronix, Roger had to get the tube from the Sony/Tektronix folks -- it was a special order. Tek itself did not make one that was high enough BW. Roger had just finished designing the 3D frame buffer for Teklabs and had used a Sony/Tek Trinitron color tube in that system - which I remember was one of the most expensive parts of the FB. Roger used its BW cousin for Magnolia, which was cheaper, but the tube and hard disk were the two most expensive parts in Magnolia. Roll the clock forward only 2-5 years. When Apollo, Masscomp, and later Sun started to make workstations, there tended to be three types of display -- a low-resolution BW, a 'paper white" high resolution, and eventually a color tube. Also in the late 70s, Motorola created the 6845 video chip, which along with a micro such as a 6502/6800/Z80, became the de jure standard for most terminals. It. and 8 2102's SRAM chips, and you had a simple (white on dark) display that worked with low-end tubes. Also, the displays were pretty expensive when IBM released the first VGA for its PC/AT. It took the VGA market taken off to start to drive the cost of the monitors down. But anything over 12-15 inches was still pretty expensive, and you needed VRAM to drive it, *etc*. My point is that Black on White does not take off with hockey stick-style growth until after the "workstations." FWIW: the 1980s Mac original display is small and not extremely high resolution compared to what would quickly come to expect. So while people liked the Xerox idea of blank on white, it was not economical. I personally did not get to start using the 'paper' paradigm until the time of the Sun-3 and like (~1985/6). As an engineer, I also remember having the default display resolution - we had more program memory, *etc*., but the tech writer would get a high-end black and white because they were working with text [*i.e*., Framemaker pages] for documents. It was in the mid-1990s that having a solid color display with high resolution became the default. But the cost of the silicon to drive it had to come down, and the market for high-end displays needed to appear. BTW: what happened? LCD came out --- why it used Silicon manufacturing techniques. So once it was perfected, the ability to make a high BW display quickly overtook the analog tube schemes. As for the current light on dark, I wonder if this is just a new set of engineers making their mark. I'm sure it's better. The cost is the same, so now it's just marketing and a way to show off being different - *e.g.*, new/cool. ᐧ On Thu, Jun 15, 2023 at 4:56 PM segaloco via COFF &lt;coff(a)tuhs.org&gt; wrote: