IBM 3270 interfacing?

From: Ethan Dicks <>
Date: Mon Nov 22 19:58:03 2004

On Mon, Nov 22, 2004 at 04:30:11AM +0000, Mike Ross wrote:
> 3270 terminals use... 3270 protocol, at the lower levels, to send noises
> down a coax wire. At the higher levels, you get into heavy-duty blue-glue
> acronyms you don't want to touch with a condom-covered bargepole. Like BSC,
> SNA... <shivers>.

Hey! I used to *make* that kind of stuff (68000-based protocol engine cards
for PDP-11s and VAXen that talked HASP, 3780, SNA...) Our SNA products would
pretend to be PU Type 2s (like a 3174) and talk to something like a 37x5
I/O front end box (PU Type 4) that was channel attached to a mainframe. Our
target market for this line was VAX users who needed to login to some
departmental mainframe somewhere, but didn't want to spend the bucks to have
an independent comms arrangement terminating in another terminal on their
desk (back when a VT100 was $1700, let alone what a real 3270 would cost).

I learned more about the bit-level detail about SNA than anyone would ever
want to, but at the time, since we didn't have a single inch of Ethernet,
it was pretty interesting (100% of our box-to-box comms were sync (DDCMP
and IBM protocols) or async (Kermit)).

> The 3174s also came with options for token ring (pretty cheap now) and
> ethernet (still ruinously expensive) attachment. Get one of those, and get
> the latest version of the controller microcode (C6.4 I think) from IBM.
> This magic microcode allows you to also use the 3174 as a telnet client -
> you boot the controller, power on any coax-attached 3270 terminals - and
> the terminal displays a screen which essentially allows you to type 'telnet
> <hostname>' and connect, like any other telnet client or serial terminal
> (but with a funky keyboard!).

Cool... that could be fun... I used to have a couple of Memorex 3270 clones
in the attic - not sure if they are still there - haven't dug that deep in
a few years. If I run across them again, that would be a neat application.

Ethan Dicks, A-130-S      Current South Pole Weather at 23-Nov-2004 01:44 Z
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Received on Mon Nov 22 2004 - 19:58:03 GMT

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