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I recently acquired an IBM 3481 terminal. It has a parallel port, a DB-15 port (I believe for a twinax-T connector), an 8P8C keyboard connector, and a PS/2 connector. Since I don't have a vintage IBM minicomputer or AS/400 to connect it to, I'd like to determine if it's possible to connect this to a modern device or network as a dumb terminal. I'm not averse to soldering or arduino, but I am averse to spending more than $200 on a solution.

EDIT: It's a twinax based 3486 variant, not 3481.

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  • The dumb terminal models were the IBM 3151 and IBM 3153.
    – Brian
    Commented Jun 12, 2020 at 18:42

4 Answers 4

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Short answer is 'no', these are pretty sophisticated terminals that speak an IBM proprietary-ish protocol, not simple old async RS-232.

Longer answer is 'maybe', depending on what you want to get out of it. Some folks pick up an IBM 3174-like controller, and if it's late enough model with new enough microcode, it can talk to something like the 'Hercules' mainframe emulator running on a Linux box. While interesting in and of itself, and a good way to learn about IBM mainframes, this doesn't sound like exactly what you're looking for or want to pay for.

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According to this site, the 3481 uses the 3270 protocol, which isn't that difficult to parse and process, but definitely not dumb.

I have seen "middleman" applications that allow to use a 3270-type terminal to interact with other applications (e.g. z/OS UNIX) which expect dumb terminals, but usage is quite different from what one is used to. It shouldn't be too hard to write such an application, but definitely time consuming.

More difficult will be the link and physical side: I couldn't find any details about the interface of 3481, but if it uses 3270-style coax, it will probably use IBMs SNA on OSI Level 3 and SDLC on OSI Level 2. Which definitely means soldering and an arduino, and writing a good bit of some kind of network-stack for it.

Physical specs are for example here. There are/were chips (called USART) that act similarly as an UART for the RS232 interface, e.g. the Intel 8251A or Zilog Z85230/Z80230/Z8523L/Z85233, but I think they'll be difficult to obtain.

If you manage to make it work somehow, please keep us informed; I'd be very interested.

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    The 8251A is kinda obscure now, but the Z85230 is still in production; you can buy them from Mouser. SDLC/HDLC sync serial is still used lots of places, so virtually all modern serial chips have some support for it, usually depending on how much they make the host CPU/MCU do.
    – KJ Seefried
    Commented Apr 9, 2018 at 20:03
  • @KJSeefried: Could you give some examples what chips you mean by "modern serial chips with some support for it"? Just so I know what I need to buy...
    – dirkt
    Commented Apr 9, 2018 at 20:08
  • The Z85230 is still is around. Newer chips, like the Zilog Z16C30 or Infineon 20542, have more smarts, but aren't a complete 3270 solution. There are a lot of chips with yet more smarts (Dallas/Maxim/Exar) with sync HDLC/SDLC engines, and things like the Infineon MUNICH supports hundreds of HDLC/SDLC channels per chip, but these are more for telco than 3270. The Am188Cx-series, Motorola Coldfire (or MC68302 and related) or 8051-variants that mate a processor with a sync serial SDLC/HDLC core that could provide a complete solution. There are hundreds of products in this space.
    – KJ Seefried
    Commented Apr 9, 2018 at 23:49
  • It's not even coax, it's twinax :(
    – 65a
    Commented Apr 11, 2018 at 15:29
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Straight answer: No. Not usable for your purpose.

The 3481 is a block mode terminal to be connected to a cluster controller and running its own (3270) protocoll. It's anything but dumb and its protocols are anything but simple.

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please check this website for an interface that is just under development...

https://deskthority.net/viewtopic.php?f=7&t=23885&sid=2355e7e42a296f71abd0dea3ef8f3e21

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  • That link is rather inflammatory.... ASCII had its problems and warts to..
    – Stefan Skoglund
    Commented Jun 14, 2020 at 12:02

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