Building an IBM 3270 terminal controller
49 points
16 days ago
| 6 comments
| ajk.me
| HN
wkat4242
15 days ago
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I love old terminals. I used to sit at the ones in the library for ages (I often managed to 'escape' into the data controller somehow :P ). And at college, all the X-Terminals were often occupied because they were the only way to run NSCA Mosaic to see this cool new "Internet" stuff. Meaning the rooms full of green screen terminals were completely deserted. I usually took two for myself (This was before I learned of Gnu Screen and tmux lol)

I still have my own VT520 <3 Not getting rid of it (my girlfriend keeps asking why do I keep that old thing around, grrr)

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Aloha
15 days ago
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My WYSE 180E is still sitting in the garage for much the same reasons.

I used that every day as my daily driver terminal for 10-12 years - I got it was what was effectively NOS, so zero hours on the tube. I've not turned it on I think in 8 or 10 years.

I'll drag it out once I clean up the garage this summer.

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wkat4242
15 days ago
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Yeah my VT520 is also very clean. Unfortunately though it's one of the later ones sold by Boundless. The same thing but not the DEC logo, and that matters a bit.

App support is pretty horrible these days though. Most apps don't bother reading termcap/terminfo anymore and just blast Xterm whatever to the terminal :) That makes the functionality a bit limited.

I did some of my best work on those terminals though. Especially because they didn't have a browser. Very distraction-free. I can see why this works out so wel for people like George R.R. Martin.

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Aloha
15 days ago
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Putting screen in the middle is actually the fix for that - Screen has been very good for me at acting as a decent translation layer for misbehaving apps.
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wkat4242
15 days ago
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Huh I never thought of that. Thanks!!
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Aloha
14 days ago
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Its one of the two reasons I've never switched to tmux - the other is habit, I have a well formed .screenrc and I'm used to it.
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wkat4242
14 days ago
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I was a screen holdout for a long time too but in the end tmux won me over :) But I still know screen very well.

So tmux doesn't do this well either? Too bad. I'm not surprised screen does it well though, with its long history.

By the way one thing that's a bit sad about the VT520 is that it looks really boring. It has a standard "VGA Monitor from the 90s" look. The great thing is that it takes standard PS/2 keyboards unlike the previous special ones. But the VT220 and VT320 looked much cooler.

Not to mention the VT05 by the way, that was straight out of star trek <3 It was deep as hell though, no way that would fit on a modern desk. It didn't even have a CPU, it was full of boards of discrete logic.

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Aloha
14 days ago
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tmux might work - I tested early with tmux but the last time I bothered was pre-1.0 versions of tmux. Screen supports it well, but tmux is probably worth testing.
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rbanffy
14 days ago
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Someday I need to procure a VT oh Wyse capable of Tektronix graphics to serve as a reference for a project I’m doing, but they aren’t easy to find on this side of the Atlantic.
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throwawayForMe2
15 days ago
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I spent a number of years pounding out code on 327x terminals. They were built like tanks.
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Aloha
15 days ago
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I'd love an actual 327x family terminal - they're very well build, and the inbuilt font set is rather visually appealing.
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tyfon
15 days ago
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I work in a bank, and we still have to drop into "3270" from time to time to modify stuff in the core.

The gui apps connected to it are just sending the data stream in the background.

Long lasting technology really.. But we're on the way to replace the core now.. Not looking forward to it tbh!

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lambdaone
15 days ago
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This is magnificent reverse engineering. I wonder why retrocomputing is so fascinating? Is it an attempt (by older people) to rediscover their youth, or is it a search for a golden age of computing where people still had some autonomy over their hardware? Or something else?
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twoodfin
15 days ago
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Personally, I’m interested in getting to learn about and play with toys that had insurmountable (to me) barriers of cost, access, or obscurity when they were contemporary.

The purest “retro” experience I’ve had wasn’t retro at all: Stepping into an MIT Athena lab a quarter century ago to see an SGI Indy ready for my login.

In a way, it’s like finding out what winning the lottery would have meant for a curious tech nerd.

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icedchai
15 days ago
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Yes. I bought an SGI O2 and a NextStation off of ebay for those reasons. I could've never afforded this stuff when it was new.
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wkat4242
15 days ago
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Ooh the O2 was a beautiful system. In fact all their systems looked amazing. Where all the others made all this super-boring businessy stuff. Well, except Sun, they had style but not too explicit, they were kinda in the middle.

But HP and IBM made boring old boxes :P I did love HP-UX though.

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icedchai
14 days ago
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I always preferred Sun hardware, myself. In the early to mid 90's, SunOS was basically the gold standard for Unix systems and building open source software. Early Solaris releases were pretty rough, but by Solaris 2.5 it was pretty good...
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wkat4242
15 days ago
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Yeah I'd love to play around with a real IBM Mainframe.

However even in these days they are expensive, plus I don't have the space or power requirements for one of those :) There's are reason they were called "big iron".

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glhaynes
14 days ago
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There's also an enjoyment in revisiting the old stuff while standing on its shoulders.

For example, there are modern games made by hobbyists for old systems that completely outclass literally anything that was available contemporaneously. Today anyone with a computer has access to development hardware, software, documentation, and community resources that are all just lightyears beyond what was available then at any price. Changing a few lines of code and instantly hopping into a cycle-accurate emulator to test takes milliseconds versus writing out floppies or EEPROMs. Arcane tricks that only a privileged few knew (if that) are now common knowledge. That stuff leads to whole other strata of capabilities being accessible.

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EvanAnderson
15 days ago
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I love machines where the complexity is such that a single person can have an almost complete understanding of the entirety of the machine. You can get that from old machines.
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blame-troi
15 days ago
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I suspect it's the same appeal as woodworking or hor rodding or living history reenactment.
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MSFT_Edging
15 days ago
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Humans also love their tools. While tools get more advanced, they sometimes lose some charm or benefits of older tools.

For me, an interest in retro tech is seeing how people did things in the past and realizing we lost some "nice" experiences along the way.

Also, in a world where everything becomes obsolete at record speeds, something so obsolete feels stuck in time.

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wkat4242
15 days ago
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> Humans also love their tools. While tools get more advanced, they sometimes lose some charm or benefits of older tools.

This is true. In summer when I sit in the dark with the windows open (hot country and no AC and I don't want to attract bugs), my 4K computer monitor is totally incapable of dimming to a level that doesn't blind me. Even with white on black/dark mode and brightness set to 0. In fact, even during the day I work with brightness 0 on that thing, it seems all monitors are optimised for max brightness these days.

Meanwhile, my old VT520 terminal has an analog brightness dial which I can turn so low that I can barely make out the letters in a pitch-black room <3

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kens
15 days ago
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The article mentions various old chips that interface to the 3270 data stream. Does anyone know what the similar chips are to interface to IBM's bus-and-tag? I saw bus-and-tag interface chips that converted the weird voltage levels a few years ago but lost the part number and haven't been able to find them since.
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kens
7 days ago
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In case anyone ends up here looking for an answer, the relevant chips are the SN75121 and SN75122 for transmission lines and the SN75123 and SN75124 for IBM 360 bus-and-tag I/O (Signetics N8T13, N8T14, N8T24). The relevant IBM spec is: https://bitsavers.org/pdf/ibm/370/channel/GA22-6974-4_360_37...
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rbanffy
14 days ago
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I wonder if a simple MCU wouldn’t be a better option to an FPGA in this case.
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AstroJetson
14 days ago
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One of the features of OS/2 was it could act as a terminal controller. One day people started having problems with their terminals. Response times were getting slower and slower and finally they ground to a halt.

From across the cube farm there was an "oh no" Turns out that our co-worker didn't attach to the dev system, he attached to the production environment. As users detached sessions and reconnected, they connected to his desktop. As his desktop got more and more sessions, they got slower and slower.

Lucky for him it was only our building, the main phone center wasn't involved.

Still think of you buddy, one of my favorite "back in the day" stories.

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