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I am considering taking my nostalgia for the eighties to the next level and getting hold of a green monochrome monitor. In particular, the nine inch monitor of the Apple IIc, but maybe something else depending on price and availability. If you put 'monochrome' into Ebay there are a number of options.

It would be good to run a terminal of my modern Debian on it, either a second monitor with the terminal in it and modern stuff on the main monitor or booting into recovery mode and running only terminal programs and commands.

This might be harder on a notebook which is limited to USB and HDMI ports, but easier on a desktop where you can perhaps the appropriate 'graphics' card, or maybe better called 'anti-graphics' card if it exists.

Does anyone know hard or time consuming it would be to achieve this? On the surface it sounds like it might be easy, since these monochrome monitors and Unix were developed around the same time, but there are possibly some details of the electronics and signal transfer which could turn it into a nasty electronics project. If there were a simple adaptor from the notebook to the monochrome monitor, I may do it, but then if you have to design and build your own circuit and circuit board would probably leave it out for now. Then there is the software side of it, such a thing is probably not going to be 'plug and play', you're going to have to tell Debian what kind of monitor it is.

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    The typical "green screen monitors on Unix" in the 70s and 80s were not monitors like the Apple IIc or even the IBM PC. They were video terminals like the VT-100 and ADM-3A and Wyse 50 - i.e., a box with some electronics (typically an 8-bit CPU and a few K of RAM) and a monitor (like th Apple IIc or the IBM PC) and a keyboard, with a serial interface to connect it to a Unix box. – manassehkatz-Moving 2 Codidact Nov 16 '20 at 4:56
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    I definitely used ADM-3A with green. But you're probably right about VT-100. Using "green screen" here in the proverbial sense - rather than saying "dumb terminal" or "glass TTY". – manassehkatz-Moving 2 Codidact Nov 16 '20 at 15:38
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    @manassehkatz-Moving2Codidact that is an interestng comment, do elaborate in a formal answer.. The Apple IIc monitor was just this cute green monitor I remember from early school days, but did not know there was something called "video terminal", different to a "monitor". I thought it was just "TV" and "monitor". Probably a green CRT in any of them is the same, but their electronics is different. The Apple IIc monitor might be cute, but these VT-100 or ADM-3A "video terminals" sound like a more purist way of having a linux terminal on a CRT. Am interested to know more about this. – cardamom Nov 16 '20 at 23:23
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    @cardamom If I get a chance, I will write up a real answer explaining it. But right now I should get some work done. Via an SSH session that emulates an ANSI terminal over the internet. – manassehkatz-Moving 2 Codidact Nov 16 '20 at 23:25
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    Maybe not what you are looking for, but cool-retro-term emulates various vintage monitors on your modern linux system. It's actually pretty cool. – evildemonic Nov 17 '20 at 18:50
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The Apple IIc monitor (A2M4043) mentioned in the question takes a composite video signal. Some older laptops and graphics cards output composite or S-Video either directly or through a breakout cable. Otherwise, an external graphics adapter that interfaces to the PC via USB and outputs VGA is about $10-15. Once you're working in the analog domain, you have a few options, such as a pre-built adapter that converts VGA to composite or S-Video for about $25-30.

Or you can take the "dumb terminal" approach. Gary Kaufman's ASCII Video Terminal (an update to Geoff Graham's original design) connects to a host PC through RS-232, outputs text to VGA and Composite, and takes a PS/2 or USB keyboard for sending commands back to the host computer.

If your monitor were VGA, I would recommend Peter Hizalev's version (full kit here for $52) with a much better font.

Personally, I'm interested in the old TTL (Hercules/MDA) monitors such as the Zenith 12 inch ZVM-122 (amber) or ZVM-123 (green) CRT, but I don't know of a good way to drive these from a modern computer. Maybe modify Peter Hizalev's code for MDA timings, find an appropriate font, and cobble up an HD-15 to DE-9 adapter?

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    Composite is fairly simple if you don't want color (which is where it gets complicated)- you can just combine the green and sync. Also worth noting the original Raspberry Pi's had a compose output and might be a reasonable choice for a moderately capable platform to put in a box intended to emulate an old system. – Chris Stratton Nov 16 '20 at 19:15
  • Converting from VGA to composite is non-trivial. VGA is non-interlaced, whereas composite is interlaced. The interlacing alone requires a frame buffer (might be a way to buffer individual lines if the vertical resolutions exactly matched; they don't). So the conversion must be digital and fairly sophisticated. – Harper - Reinstate Monica Nov 16 '20 at 19:54
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    You can get a USB VGA output adapter like this and then from there plug that into a VGA to composite converter. Total cost <$50. – Doktor J Nov 16 '20 at 21:53
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    Thanks, a little bit of soldering for one of these kits could be a bit of fun. Will avoid the dumb terminal, looked up what that was, no on-screen editing, no utf-8. Sometimes working with embedded devices it was like that and not fun. My old notebook had a circular S-video socket but for this one will have to connect adaptors to usb. Your hercules monitor looks like a TV with a speaker on the side.. Actually @Doktor J, those two products connected together look like they will do the job. – cardamom Nov 16 '20 at 23:42
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    You could certainly get AGP graphics cards with S-video out (ATI - I've got one somewhere). eBay seems to have PCIe with S-video, e.g. Radeon HD 3450; then conversion is easy (especially as you can discard the chroma channel) – Chris H Nov 17 '20 at 14:40
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Does anyone know hard or time consuming it would be to achieve this?

Assuming you have a modern PC with VGA out, or you can put in a graphics card with VGA out, it's not hard at all, if you know a bit about how this works.

You need to look up the horizontal and vertical sync frequencies that your monitor operates with (use the documentation, or google for online documentation, or if you know it was connected to e.g. an Apple II, then use those). Often the old monitors only worked at exactly these frequencies, and using others (in particular higher ones) could be dangerous for the monitor and even destroy some of the earlier monitors. So be careful.

Then you need to program the graphics card to use those frequences. On Linux, with X, this is done with a modeline; there are plenty of tutorials and tools that help you making one. On Windows, it's more tricky, and I'd have to google that, but I'd assume it can still be done editing some configuration files, or the registry.

On the hardware side, you'll probably need a VGA converter to whatever input (e.g. coax) your monitor uses. Simplest way would be to just use one color channel (e.g. the green one). You can make those yourself with a bit of soldering skills.

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  • The Windows equivalent is probably a custom .inf file for the monitor. – Alan B Nov 16 '20 at 7:21
  • @AlanB If these still exist in modern Windows; I haven't looked at those in years, so I tried to be conservative. – dirkt Nov 16 '20 at 9:34
  • The windows nvidia driver GUI interface allows for custom-set modes. I have not used it however – Yorik Nov 17 '20 at 20:55
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VGA was a huge and very bold rejection of NTSC!

TLDR of this whole history section: VGA and NTSC have nothing to do with each other. VGA was a blank-sheet design that smashed NTSC limitations with extreme prejudice - and planned to never, ever, ever go back.

Apple IIc monitors, like most monitors of that age, use the NTSC composite video standard in all respects that are not incompatible with their purpose. For instance monochrome displays do not use the color modulation obviously. S-video displays deliver luma and chroma separately. RGB delivers R G and B as three separate monochrome channels. Other than that, they are NTSC through and through.

These were tentative tiptoes away from traditional NTSC; they stayed with the standard in all other respects - frame rate, scan line rate, timing and screen dimensions. This frustratingly limited screen resolution, right up until VGA finally smashed the "glass ceiling": it threw away NTSC altogether and started with a blank-sheet new design. The word was "we will no longer support using your TV as a display device; get a dedicated PC monitor".

And THAT required the market to shift from "basically everyone using TVs as their display" in 1977 to "almost everyone using a dedicated PC monitor" - and remember at the time, monochrome monitors were $200-300 and color monitors were $700. Even in the mid-1980s, the need to drive a TV had strong sway - can you imagine the PCjr shipping with no ability to connect it to a TV? Impossible!

The only company ever to get away with smashing the NTSC monolith was IBM, with their niche Monochrome Display Adapter (MGA) in 1981 (~350 scan lines per field instead of the usual 200).

So again it was IBM to introduce original VGA (640x480 non-interlaced per field), with their meant-to-be-revolutionary Personal System/2 (PS/2) line. IBM was correct that nobody in the business world cared about TV support and would not object if asked to pay $700 for a dedicated-to-purpose color monitor. The goal of VGA was to entirely free computer displays from the albatross of NTSC limitations. No NTSC support was even imagined; the goal was to leave NTSC in the dust.

*But mind you, 1987 was also when the Amiga was starting to "find its feet" in the marketplace. Heck, Amiga's Video Toaster launched in 1991 and wound up becoming the king of midsize TV production for the whole decade - a lot of local TV markets used the Video Toaster for graphics and fonting of news, commercial production - Amigas even did the CGI on Babylon-5.

But the market message was clear: All-in, or all-out of NTSC. No more "stuck in the middle", no more "NTSC albatross dragging down PC resolutions".

It isn't resistors

As such, there are only 2 ways to get from a VGA output to an NTSC-family display:

  • Use a frame buffer
  • Have the video card be versatile enough that you can change its parameters to actually output NTSC timing signals, even though they will be RGB of course. From that point it's simply a matter of mixing the sync and luminance signals correctly, and yeah, that you can do with analog circuitry... but only if the video card is able to do all the heavy lifting because its designers were extra clever and provisioned the ability to do that weird old thing.

Really, you're better off starting from scratch

The right way to solve this problem, really, is to have a USB or Lightning attached external GPU that inherently outputs NTSC composite/EGA/TARGA-24. StackExchange is not a product-recommendation site, but I gotta imagine somebody makes or made such a thing, for old-school TV production if nothing else. Technologically, it would be little more than a dongle. Far cry from the stacked/stuffed TARGA-24 boards!

Then, appropriate video drivers so your Linux/Windows/Mac system can see it as "just another display" like it does with other GPUs.

This GPU certainly could maintain a 533++ x 400 internal buffer. With monochrome NTSC displays, there is no inherent limit to the number of horizontal lines, depending on how you feel about pixels being square. And if the display supports interlacing, you can also get 400 vertical resolution, although picture elements would need to be at least 2px wide (so they are present on both fields) or they would flicker.

Keeping in mind that most NTSC-era computers outputted a non-interlaced signal 200 pixels tall x 280-320 horizontal. Interlaced TVs were able to tolerate this. Most likely, your Apple IIc monitor has the same vertical sweep hardware as other TVs of the day, and would accept interlacing.

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  • Back in the 1990s, I programmed a VGA card to produce NTSC-frame-rate video, and I don't think there was anything particularly special about the card in question. The VGA uses a controller similar to a 6485, but if memory serves, some values like horizontal character total that were limited to 7 bits on the 6485 were implemented as 8 bits, and in at least one of the display modes, adjusting the horizontal total to a value just short of 15.75KHz would yield a roughly-15.75kHz horizontal scan rate. – supercat Nov 17 '20 at 17:14
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    Strangely we're now back at the point where I can use the same screen for either watching broadcast TV or as my computer monitor... – Neil Nov 17 '20 at 18:52
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    @Neil I know. We were so log-jammed, we couldn't step away from NTSC until one standard had enough market acceptance. And then everybody jumped on it, including TV itself in the end lol. Well, next thing, now they want to send polygons! Steam tells me the only way I can play 32-bit games on my 10.15 Catalina Mac is by using it as a "dumb terminal' (well, GPU, keyboard and mouse) for my 10.10 Yosemite Mac where the 32-bit game can actually run. – Harper - Reinstate Monica Nov 17 '20 at 19:21
  • @Neil: I wonder what fraction of TV sets' tuners will ever be used within those sets' lifetimes? – supercat Nov 17 '20 at 23:09
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Creating a composite signal for a monochrome monitor should be quite easy.

I remember using 4 or 5 resistors to mix green, brightness, HSync and VSync from a 9-pin EGA output to construct a perfectly usable composite video signal.

You will probably not find CGA or EGA adapter in 2020, but the standard 15-pin VGA looks almost as easy.

The timing in VGA is programmable. 31.5kHz interlaced is trivial to construct as a modeline in Xorg and if you want Windows, a lot (all?) of video drivers have something resembling modelines in their INF files. HSync and VSync should be made positive.

The three luminosity signals of VGA are 0-0.7v @ 75 ohm that are acceptable in the composite signal, except that you have to mix in hsync/vsync at 1v and they come in TTL level. You'll have to use 2 diodes and a few resistors.

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    That works because EGA had more sophisticated color rendition and RGB output, but otherwise remained faithful to all aspects of the NTSC standard, specifically so that composite video output would remain possible. That's a far, far cry from what VGA does, which is throw all aspects of the NTSC standard in the trash and start over blank-sheet, RGB-only with their own screen dimensions. – Harper - Reinstate Monica Nov 16 '20 at 19:58
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    "faithful to all aspects of the NTSC standard" = H/V timing and bandwidth, both of them predate the color TV. It was CGA that cared for NTSC phase peculiarities. VGA has programmable timing and NTSC timing (including interlacing) is well within the programmable range. I still don't see why it shouldn't work. Luminosity signal is exactly what composite expects - 0v for black and 0.7v for max luminosity. One have to only add 1v pulses for H/V (they are 5v in VGA, resistors are easy) and our pretty monochrome composite signal is ready. Just don't expect much of a horizontal resolution. – fraxinus Nov 16 '20 at 22:16
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Raspberry Pi has composite video out built in. There's a QA here which has details relevant to configuration.

One of those with the appropriate adapter/cable may be the easiest way to get that old-fashioned experience you're looking for.

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There are some solutions you could try. You can search for a monochrome VGA (actually they are multisync monitors. Search on ebay for an IBM 4707 or an IBM 8503/8504 for that 90s look. While you are at it and are lucky you could find a complete PS/2 you could use as a terminal or even try to run an older version of Linux of it (Model 90 were 486 and pentiums, so provider you have 80 floppies handy you colud install Slackware on it, as I did in the 90s). Otherwise old DOS terminal emulator are available.

VGA green monochrome monitors were avaliable at the time, but weren't so common, but there were some Olivetti models or some unknowns Taiwanese brands.

You could also use as a second monitor for your main computer. There were some monochrome super VGA monitors that were used in typographies, they are lesser iconic but they do the work too.

If you have a monochrome composite monitor, like the ones were used on Apple II and Commodore computers, you could use the composite out of a Raspberry Pi then attach a keyboard and you have another fully fledged computer with Linux on it.

You could force a "true" VGA to sync at NTSC or PAL frequencies, but it's tricky and depends on how the legacy part of the video board is made.

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  • IBM PS/2 55 ? Can even run early AIX. – Stefan Skoglund Mar 15 at 1:35

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