Editing IBM 3270 (section)

=== Controllers ===
[[File:IBM 3174 controller.jpg|thumb|IBM 3174 controller]]
[[File:IBM 3174-1L as terminal of Primary Server of Biblioteca Nacional (Front) (1).jpg|thumb|IBM 3274-41D controller with terminal]]
* 3271 remote controller
* 3272 local controller
* 3274 cluster controller (different models could be channel-attached or remote via [[Binary Synchronous Communications|BSC]]  or [[Synchronous Data Link Control|SDLC]] communication lines, and had between eight and 32 coaxial ports)
* 3174 cluster controller{{sfn|3174 Introduction|loc=Ch. 1. Introducing the 3174 Establishment Controller - Figure 1-1 Overview of the IBM 3174 Establishment Controller Attachment|p=[http://bitsavers.org/pdf/ibm/3174/GA27-3850-0_3174_Establishment_Controller_Introduction_Apr89.pdf#page=13 1-2]}}

On the 3274 and 3174, IBM used the term '''configuration support''' ''letter'', sometimes followed by a release number, to designate a list of features together with the hardware and microcode needed to support them.

By 1994 the 3174 Establishment Controller supported features such as attachment to multiple hosts via [[Token Ring]], [[Ethernet]], or [[X.25]] in addition to the standard channel attach or SDLC; terminal attachment via [[twisted pair]], Token Ring or Ethernet in addition to 3270 coaxial; and TN3270. They also support attachment of asynchronous ASCII terminals, printers, and plotters alongside 3270 devices.<ref>{{cite book|last=IBM Corporation|title=3174 Establishment Controller/Networking Server Installation Guide|year=1994|url=http://www.redbooks.ibm.com/redbooks/pdfs/gg243061.pdf|archive-url=https://web.archive.org/web/20160302094553/http://www.redbooks.ibm.com/redbooks/pdfs/gg243061.pdf|archive-date=2016-03-02}}</ref>

==== 3274 controller ====
IBM introduced the 3274 controller family in 1977, replacing the 3271–2 product line.

Where the features of the 3271–2 was hardcoded, the 3274 was controlled by its microcode that was read from the 3274's built-in [[8" floppy drive]].

3274 models included 8, 12, 16, and 32 port remote controllers and 32-port local channel attached units. In total 16 different models were over time released to the market. The 3274-1A was an SNA physical Unit type 2.0 (PU2.0), required only a single address on the channel for all 32 devices and was not compatible with the 3272. The 3274-1B and 3274-1D were compatible with the 3272 and were referred to as local non-SNA models.

The 3274 controllers introduced a new generation of the coax protocol, named Category A, to differentiate them from the Category B coax devices, such as the 3277 terminal and the 3284 printer. The first Category A coax devices were the 3278 and the first color terminal, the IBM 3279 Color Display Station.<ref>{{cite web |first=Ken |last=Shirriff |title=Inside an IBM/Motorola mainframe controller chip from 1981 |date=July 2024 |url=http://www.righto.com/2024/07/ibm-3274-keystone-chip.html}} </ref>

Enabling backward compatibility, it was possible to install coax boards, so-called 'panels', in groups of 4 or 8 supporting the now older Category B coax devices. A maximum of 16 Category B terminals could be supported, and only 8 if the controller were fully loaded with a maximum of 4 panels each supporting 8 Category A devices.

During its life span, the 3274 supported several features including:

* Extended Data Stream
* Extended Highlighting
* Programmed Symbol Set (PSS)
* V.24 interfaces with speed up to 14.4&nbsp;kbit/s
* V.35 interfaces with speed up to 56&nbsp;kbit/s
* X.25 network attachment
* DFT – Distributed Function Terminal
* DSL – Downstream load for 3290 and 3179G
* 9901 and 3299 multiplexer
* Entry Assist
* Dual Logic (the feature of having two sessions from a CUT mode display).

==== 3174 controller ====
IBM introduced the 3174{{sfn|3174 Introduction}} Subsystem Control Unit in 1986, replacing the 3274 product line.

The 3174 was designed to enhance the 3270 product line with many new connectivity options and features. Like the 3274, it was customizable, the main difference was that it used smaller (5.25-inch) diskettes than the 3274 (8-inch diskettes), and that the larger floor models had 10 slots for adapters, some of them were per default occupied by channel adapter/serial interface, coax adapter, etc. Unlike the 3274, any local models could be configured as either local SNA or local non-SNA, including PU2.1 (APPN).
<!-- Or did you need 3174-11L? -->

The models included: 01L, 01R, 02R, 03R, 51R, 52R, 53R, 81R and 82R.

The 01L were local channel attached, the R models remotely connected, and the x3R Token Ring (upstream) connected. The 0xL/R models were floor units supporting up to 32 coax devices through the use of internal or external multiplexers (TMA/3299). The 5xR, models were shelf units with 9 coax ports, expandable to 16, by the connection of a 3299 multiplexer. The smallest desktop units, 8xR, had 4 coax ports expandable to 8, by the connection of a 3299 multiplexer.

In the 3174 controller line IBM also slightly altered the classical [[BNC connector|BNC]] coax connector by changing the BNC connector to DPC – Dual Purpose Connector. The DPC female connector was a few millimeters longer and with a built-in switch that detected if a normal BNC connector were connected or a newer DPC connector was connected, thereby changing the physical layer from 93 ohm unbalanced coax, to 150 ohm balanced twisted-pair, thereby directly supporting the IBM Cabling system without the need for a so-called red balun.

Configuration Support A was the first microcode offered with the 3174. It supported all the hardware modules present at the time, almost all the microcode features found in 3274 and introduced a number of new features including: Intelligent Printer Data Stream (IPDS), Multiple Logical Terminals, Country Extended Code Page (CECP), Response Time Monitor, and Token Ring configured as host interface.

Configuration Support S, strangely following release A, introduced that a local or remote controller could act as 3270 Token-Ring DSPU Gateway, supporting up to 80 Downstream PU's.

In 1989, IBM introduced a new range of 3174 models and changed the name from 3174 Subsystem Control Unit to 3174 Establishment Controller. The main new feature was support for an additional 32 coax port in floor models.

The models included: 11L, 11R, 12R, 13R, 61R, 62R, 63R, 91R, and 92R.

The new line of controllers came with Configuration Support B release 1, increased the number of supported DSPU on the Token-Ring gateway to 250 units, and introduced at the same time 'Group Polling' that offloaded the mainframe/VTAM polling requirement on the channel.

Configuration Support B release 2 to 5, enabled features like: Local Format Storage (CICS Screen Buffer), Type Ahead, Null/Space Processing, ESCON channel support.

In 1990–1991, a total of 7 more models were added: 21R, 21L, 12L, 22L, 22R, 23R, and 90R. The 12L offered ESCON fibreoptic channel attachment. The models with 2xx designation were equal to the 1xx models but repacked for rackmount and offered only 4 adapter slots. The 90R was not intended as a coax controller, it was positioned as a Token Ring 3270 DSPU gateway. However, it did have one coax port for configuring the unit, which with a 3299 multiplexer could be expanded to 8.

The line of controllers came with Configuration Support C to support ISDN, APPN and Peer Communication. The ISDN feature allowed downstream devices, typically PC's, to connect to the 3174 via the ISDN network. The APPN support enabled the 3174 to be a part of an APPN network, and the Peer Communication allowed coax attached PC's with 'Peer Communication Support' to access resources on the Token-Ring network attached to the 3174.

The subsequent releases 2 to 6 of Configuration Support C enables support for: Split screen, Copy from session to session, Calculator function, Access to AS/400 host and 5250 keyboard emulation, Numerous APPN enhancements, TCP/IP Telnet support that allowed 3270 CUT terminals to communicate with TCP/IP servers using Telnet, and at the same time in another screen to communicate with the mainframe using native 3270. TN3270 support where the 3174 could connect to a TN3270 host/gateway, eliminating SNA, but preserving the 3270 data stream. IP forwarding allowing bridging of LAN (Token-Ring or Ethernet) connected devices downstream to the 3174 to route IP traffic onto the Frame Relay WAN interface.

In 1993, three new models were added with the announcement of Ethernet Adapter (FC 3045). The models were: 14R, 24R, and 64R.

This was also IBM's final hardware announcement of 3174.

The floor models, and the rack-mountable units, could be expanded with a range of special 3174 adapters, that by 1993 included: Channel adapter, ESCON adapter, Serial (V.24/V.35) adapter, Concurrent Communication Adapter, Coax adapter, Fiber optic "coax" adapter, Async adapter, ISDN adapter, Token-Ring adapter, Ethernet adapter, and line encryption adapter.

In 1994, IBM incorporated the functions of RPQ 8Q0935 into Configuration Support-C release 3, including the TN3270 client.<ref>{{cite manual
 |       title = Using 3174 in TCP/IP Networks
 |          id = GG24-4172-00
 |        date = June 1994
 |     section = Ch. 9. 3174 TCP/IP Enhancements RPQ 8Q1041 — 9.7 TN3270
 | section-url = http://bitsavers.org/pdf/ibm/3174/GG24-4172-0_Using_3174_in_TCP_IP_Networks_Jun94.pdf#page=298
 |       pages = 269–272 (298– in PDF)
 |         url = http://bitsavers.org/pdf/ibm/3174/GG24-4172-0_Using_3174_in_TCP_IP_Networks_Jun94.pdf
 |        series = Redbooks
 |   publisher = IBM
 }}
</ref>

====Non-IBM Controllers====
=====GTE=====
The GTE IS/7800 Video Display Systems used one of two nominally IBM compatible controllers:

* 7801 (remote, 3271 equivalent)
* 7802 (local, 3277 equivalent)

=====Harris=====
The Harris 8000 Series Terminal Systems used one of four controllers:

* 8171 (remote, 3271 equivalent)
* 8172 (local, 3277 equivalent)
* 8181 (remote, 3271 equivalent)
* 8182 (local, 3277 equivalent)
* 9116
* 9210
* 9220

=====Home grown=====
An alternative implementation of an establishment controller exists in form of OEC (Open Establishment Controller).<ref>{{Cite web|url=https://ajk.me/building-an-ibm-3270-terminal-controller|title = Building an IBM 3270 terminal controller| date=May 23, 2020 }}</ref><ref>{{Cite web|url=https://github.com/lowobservable/oec|title=Oec|website=[[GitHub]] |date=October 4, 2021}}</ref><ref>{{Cite web|url=https://github.com/lowobservable/coax|title = Coax| website=[[GitHub]] |date = October 16, 2021}}</ref><ref>{{Cite web|url=https://github.com/lowobservable/pytn3270|title = Pytn3270| website=[[GitHub]] |date = October 4, 2021}}</ref> It's a combination of an [[Arduino]] [[Arduino#Shields|shield]] with a [[BNC connector|BNC]] connector and a [[Python (programming language)|Python]] program that runs on a [[POSIX]] system. OEC allows to connect a 3270 display to IBM mainframes via TN3270 or to other systems via [[VT100]]. Currently only CUT but not DFT displays are supported.

=====Memorex=====
Memorex had two controllers for its 3277-compatible 1377; the 1371 for remote connection and the 1372 for local connection.<ref>{{cite web
 |    title = 1371/1372 REMOTE/LOCAL CONTROLLER BUSINESS PLAN
 |       id = MRX 19780928
 |     date = September 28, 1978
 |      url = http://mrxhist.org/docs/MRX%2019780928%201371%20Business%20Plan.pdf
 | publisher = COMMUNICATIONS GROUP MEMOREX CORPORATION
|website=Memorex History and Memorabilia
 }}
</ref>

Later Memorex offered a series of controllers compatible with the IBM 3274 and 3174

* 2074
* 2076
* 2174
* 2274