2:3 Scale VT100 Terminal Gets Closer To Its Roots

When [Michael Gardi] finished his scaled down DEC VT100 replica a few months ago, he made it very clear that the project was only meant to look like a vintage terminal on the outside. A peek into the case revealed nothing more exotic than a Raspberry Pi running its default operating system, making the terminal just as well suited to emulating classic games as it was dialing into a remote system. But as any hacker knows, some projects end up developing a life of their own.

It started simply enough. The addition of an RS-232 Serial HAT to the Raspberry Pi meant that the 3D printed VT100 could actually operate as a serial terminal using software such as minicom. Then [Lars Brinkhoff] got involved. He loved the look of the printed VT100, and thought it deserved better than a generic terminal emulator. So he went ahead and started developing a custom terminal simulator for it to run.

Reliving those CRT glory days.

The idea here is that an an 8080 emulator actually runs an original VT100 firmware ROM, warts and all. It makes all the beeps and chirps you’d expect from the real hardware, and there’s even some OpenGL trickery used to mimic an old CRT display, complete with scan lines and a soft glow around characters.

Naturally the visual effects consume a fair amount of processing power, so [Lars] cautions that anything lower than the Pi 4 will likely experience slowdowns. Of course, nothing is stopping you from running the simulator on your desktop machine if you’re looking for that classic terminal experience.

Did this gorgeous recreation of the VT100 need to have a true serial interface or a simulator that recreates the unique menu system of the original? Not at all. Even without those additions, it blew us away when [Michael] first sent it in. But are we happy that these guys have put in the time to perfect this already stellar project? We think you already know the answer.

42 thoughts on “2:3 Scale VT100 Terminal Gets Closer To Its Roots

    1. When the VT100 was announced, PDP-8 was already obsolete. For the true PDP-8 experience you want a VT52, or an ASR33. A PDP-11 would be an appropriate system to hook up to a VT109.

      1. I realize there is a bit of a temporal displacement here, but the advantage of being a time traveler from the future is that I get to pick and choose the coolest technologies ;-)

        1. Well then you really want to get an Ann Arbor Ambassador, the finest terminal from that era. It has 60 lines and some really nice escape sequences for area scrolling that make slow modems much more tolerable. Last I checked, gnu emacs still has custom scrolling routines for the AAA.

      2. “when the vt100 was announced, pdp-8 was already obsolete.”

        decmate iii+ was produced until 1990, well past the 1983 introduction of the vt-220, successor to the vt-100.

      3. “PDP-8 was already obsolete.” LOL! Hey, I saw a PDP-8 running a light show at Earthquake Ethel’s in Portland long after the VT100 was in service. I didn’t say that either one of them should be NEW.

    2. Wasn’t the default pdp-8 terminal a VT-52 or something like that?

      I don’t know as I’ve never used one – we used VT-100s at Uni though :-) Very clacky keyboards ;-)

      1. the pdp-8 had such a long life that it lived through teletypes, vt-52s, vt-100s and beyond. the vt-78 was a vt-52 with a built-in pdp-8. the decmate was a vt-100 with a built-in pdp-8. decmate ii and decmate iii looked more like vt-220s (they weren’t vt-220s with a pdp-8 built-in; they had built-in video circuitry that used the same monitor and keyboard as the dec rainbow).

        1. Decmate systems are not PDP 8 and they are not hardware compatible. They are emulating the PDP 8 and were sold to legacy customers who did not want to upgrade. If a Decmate is a PDP 8 then a Raspberry Pi is also a PDP 8, both are hardware incompatible emulations.

  1. Oh, but for true realism doesn’t it need to have ghostly character blocks burned into the simulated phosphor ;-) ?

    Or better still, the simulated VT-100 display starts out OK, but over the course of a long hacking session gradually burns characters in until nothing is readable. Then you have to stop with the Jolt Cola and crash onto the adjacent mattress until 2pm the following day!

    But actually, it does look like a really great project – respect!

    1. “Oh, but for true realism doesn’t it need to have ghostly character blocks burned into the simulated phosphor ;-) ?” Cool-Retro-Term has some of these features, actually! It’s a shell/CLI for *nix systems. Running minicom inside is no problem, at all. 🙂

    1. Because you can easily burn down your house if you mess up the flyback power supply. Rip apart an old terminal and check out the scorched PCB in the high voltage section. You don’t want these things in your house.

      1. And because the understanding of tube technology is on the decline. Except among tube/vintage/audio fans, of course. It’s merely an assumption, but I sometimes think that the concept of high-voltage also has become sorta alien to many of us. Maybe LCDs are safer, also. Accidents involving high-voltage harmed a lot of experienced/inexperienced people in the past.

        In German, there’s a term for it, I think. It’s “Schwachstromelektriker” (translates to weak current electrician). It describes a person that usually works with low power/low voltage only. Approximately up to 12v DC, or at least below 60v or so, not sure. It’s also sort of an insult, though, it seems, according to the web, because it describes a simple minded person. Anyway, most thinkerer will likely think of the technical meaning first.

        Personally, I think that a CRT from a b/w camping TV could fit just fine in such miniature projects..

        1. can you even still get those, with the shutdown of analog broadcast TV? (not that anybody could really stop you if you wanted to run a low-power ( < 50W or smth) recast in your neighborhood)

      2. If you wanted to make a scale replica with a CRT, the cheap 5″ B&W portable sets from the early 2000s are still readily and inexpensively found on fleabay and thrift stores.
        A “secret source” of 12-14″ monochrome tubes is the “word processor”. These had amber, green, and sometimes paperwhite displays. They usually received very little use and can still be found for under $100.

        1. Excellent tip!

          I spent many years repairing TVs.

          The real safety issues are complex and too much for a post here.

          Just buy 2 little portable black and white portable TVs with composite input. The second as a replacement if when the first fails.

          Put some green or amber tint film over the screen. Black and white TVs have shorter phosphor persistence because that are made for fast moving images so you won’t have quite as much “glow” but if you know how to do so safely you could simulate this a little by adjusting the focus.

  2. “Naturally the visual effects consume a fair amount of processing power, so [Lars] cautions that anything lower than the Pi 4 will likely experience slowdowns.”

    the vt-100’s 8080 was only running at 2 megahertz, so it had to xoff at the drop of a hat anyway. slowdowns are par for the course.

    1. Older systems did not handle flow control very well so they added lots of nul bytes for “padding” after each escape sequence, termcap lets you specify how many nul chars you need. The AAA was really slow, needed crazy amounts of nuls.

    1. Well, yes and no. Monochrome CRTs, at least, were very lightweight. Just think of MDA/Hercules monitors from the 80s. Or these small monochrome VGA monitors that could be found in cash registers. Or black/white portable TVs (or camping tvs). In comparison to their size, they feel like there’s nothing in the chassis.

      The high-voltage thing is a valid objection.
      Only experienced people should work with that.
      Personally, I think It’s always better if a second person is around that can reanimate and call the ambulance in case the electrician dude gets a shock followed by a heart attack. High-voltage, especially if it’s clocked/AC, always demands respect and carefulness.

    2. If CRT is dangerous then by extension any product with mains power inside is dangerous. Most CRT displays have a bleeder resistor which automatically discharges the tube (you can usually hear it when you shut it off). The potential shock from the tube is like a Leyden jar – painful, but just a static charge.

      1. A TV tube (CRT) is like a big high voltage capacitor. The larger the tube the larger the capacitance.

        A charge tube can give enough of a shock to throw you across a room.

        Even this can be fatal from the injuries potentially caused.

        In the time (many years) that repaired TVs, I never saw one with an obvious HT bleeder resistor. If there was one it would be in the flyback transformer where it has high potential to fail and wouldn’t be at all obvious. So in any case you would have to treat the TV as if it doesn’t have a bleeder for safety reasons.

        And yes, any product with mains voltage (240 V AC in my country) is dangerous, there’s a warning in the back.

  3. I remember being bored rigid at work staring at my vt100. I passed a few hours pressing the left / right arrow key in setup mode so the cursor moved across continuously. I would see how many “T” tabs I could clear on each pass. Ending a pass with fewer tabs than I started with was success, more tabs at the end meant failure and being caught by the boss was very embarrassing. Glory days.

    1. FWIW it /might/ be fine, depending on what you’re attaching it to.

      Obviously you want a level converter to spare the Pi’s 3.3v UART from being toasted by 5v or 12v UARTs. But I’ve heard that many modern devices don’t tend to have true RS-232 voltages or voltage swing anyway. So if the thing you’re connecting it does serial with 0v/5v or 0v/12v, then a MAX-232 isn’t strictly necessary though it might be tolerated with not trouble by the computer end.

  4. Having dealt w terminals on Tandem, IBM TSO, Mohawk systems and a cranky NCR fiche printer. I can appreciate the effort, but don’t see the appeal. (not even w properly marked PF keys…lol)

  5. Pro tip: X11 (and all of the GUI development tools I know of) allows you to create windows that don’t have the usual window decorations, even in full screen, even when there’s a window manager running. Those anachronistic Ubuntu decorations spoil the effect.

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