Differentiating IBM 3101, 3270 & 5250 terminal keyboards

The IBM 3101 ASCII Display System, 3270 Information Display System and 5250 Information Display System were three major product families that originated in the 1970s that possessed many terminals from the '70s, '80s and '90s. Whilst at first the three major families were easily distinguishable when they used IBM Model B keyboards, IBM later introduced new terminals with keyboards or outright keyboard replacements for existing terminals from the Model F and Model M families that could share the same keyboard tooling. As a result, an analysis of the layout is required to identify what family of host system the keyboard belonged to when other documentation such as a part number or its host are missing. This identification guide topic will demonstrate how you can do for keyboards of the '70s, '80s and '90s if you're not familiar with terminal keyboard layouts.

Contents

Background

The IBM 3270 Information Display System was launched in 1971 as a family of coaxial cabled terminals that during this time usually connected to IBM System/360 or System/370 mainframes. It ultimately included many terminals introduced from 1971 to 1979 such as the IBM 3275 Display Station, 3276 Control Unit Display Station, IBM 3277 Display Station, 3278 Display Station and 3279 Color Display Station. The IBM 5250 Information Display System launched in April 1977 alongside the IBM 5340 System/34 midrange computer they were supposed to operate with as a family of twinaxial cabled terminals. At launch, the 5250 series included the IBM 5251 Display Station and 5252 Dual Display Station. Despite its numerically less model number, the IBM 3101 ASCII Display Terminal was rolled out last in October 1979 as an RS-232C and RS-422 terminal known to be used with IBM Series/1 minicomputers and the IBM 8100 Information System. Whilst 3101 doesn't have a family name as one might assume [like "IBM 3100"] but it in fact spawned many compatible terminals in the '80s just like the other two families.

Due to the fact IBM used unique keyboard assembly designs for all three families during the Model B era, it's extremely easy to differentiate them. However, for the compatible but visually different terminals introduced for all three families in the '80s, the keyboard designs become much more unified as a possible effort to suppress cost by reducing the number of unique keyboard assembly designs in production. As a result, the number of unique designs per terminal family declined and a handful of unified designs emerged that differed only by what text and symbols are printed onto the keycaps.

Model B keyboards

The IBM Model B family was the premier IBM keyboard in a time (approximately 1972 to 1981) where each new [group of] system IBM released likely had its own unique keyboard design. Each of the three major families used its own unique shell and assembly designs that allow one to tell them apart in an instant.

3101

The IBM 3101 was the last of the three major families to be introduced, thus the IBM 3101 ASCII Display Terminal itself is the sole 3101 product in the 1970s and had a single keyboard design - the 3101 type Model B. This keyboard always had a breadbin/breadbox-like appearance with two columns of separated keys on the left-hand side and a rectangular compartment for dip switches on its forehead.

3270

The IBM 3270 was the first of the three major families to be introduced, thus it's no surprise that even for the 1970s era there's some diversity to be found. Although thankfully, they're still unique keyboard designs for the 3270 series that make contrasting them all against 3101 and 5250 compatible terminal keyboards easy. The IBM 3275 and 3277 Display Stations of the early 1970s had two Model B keyboard styles known as Type B, the 327X-66 type Model B and 327X-78 type Model B, which are both short and long versions respectively of the same design. (There was also an earlier Type A version of the keyboard with Micro Switch SW key-switches that looked very similar and subject to the same observations). These had a breadbin/breadbox-like appearance with just one column of separated keys on the lefthand side.

Later in the 1970s, IBM introduced a refresh to the 3270 line-up with the IBM 3276 Control Unit Display Station and IBM 3278 Display Station. IBM later added to the family the IBM 3279 Color Display Station, the 3270-compatible IBM 3251 Graphics Display Station and IBM 8775 Display Terminal, and operator console versions of the IBM 3278 (Model 2A) and IBM 3279 (Model 2C). This resulted in three new types of keyboards - the 327X-75 type Model B and 327X-87 type Model B most of the aforementioned terminals used and the 327X-OC type Model B that the IBM 3278-A2 Display Console and IBM 3279-2C Color Display Console used (and was technically an option for IBM 3276). Collectively, IBM called these keyboards IBM Base Keyboards. All three types can be recognised for their unique access panel in their palm rest that stores the host terminal's Problem Determination Guide but the former two types are also notable for their distinct cutout on their forehead region.

5250

The IBM 5250's terminals could have two Model B keyboards - the 525X-66 type Model B for data entry and 525X-83 type Model B for typewriting. They always had a breadbin/breadbox-like appearance with two columns of separated keys on the left-hand side, large bezels from the keys to the sides, a distinct rectangular recess on its forehead, and for the 83-key version the alphanumeric and keypad keys were not separated.

Early Model F keyboards

The practice of introducing a new keyboard design for each new terminal almost continued into the Model F era when the IBM Model F family succeeded the Model B in 1981, but the practice was effectively ended by early 1984. However, there are a couple of examples that did make it to market to discuss. Generally, the designs for each of the three families are still unique but the seeds of unifying the keyboard designs are already apparent.

3101

From 17th August 1984, IBM started shipping IBM 3101 ASCII Display Station models 230 and 855 and IBM 7485 Display Stations with a then-new Model F-based keyboard to replace the original 3101 type Model B keyboard^[14][14]
IBM - IBM 3101/7485 Display Stations Enhanced Brief Description of Announcement, Charges, and Availability (#184-154) [accessed 2023-01-20].. This new keyboard is based on the design of the 3270-family 31XX-87 type Model F seen below that was already in production a year and a half before but thankfully has one obvious difference - the lack of the characteristic blue switch.

3270

In December 1982 and March 1983, IBM announced the first in a long line of lower-cost 3270 family terminal replacements with the IBM 3104 Display Terminal and IBM 3178 Display Station respectively. Both terminals had multiple variants, including B1/C1, B2/C2, C3 and C4. B1/C1 received a 31XX-75 type Model F (75-key data entry) keyboard and the rest received 31XX-87 type Model F (87-key typewriter) keyboards. Layout-wise, they were based on the 327X-75 and 327X-87 type Model B keyboards and were likewise considered to be apart of the IBM Base Keyboard family. IBM 3104/3178 keyboards are known as "blue switch" Model Fs in the keyboard community due to their signature blue-coloured switch used for toggling the terminal's display between mixed-case or uppercase-only characters.

5250

The first well-known terminals that featured Model F keyboards were the IBM 5291 Display Station and IBM 5292 Color Display Station. The IBM 5291 Model 1 was mentioned in IBM literature as early as December 1981^[16][16]
IBM - IBM 5291 Display Station Setup Procedure (#GA21-9408-0) [accessed 2023-01-21]. License/note: document archived by bitsavers. and the 5292 Model 2 came a little later in September 1982^[17][17]
IBM - IBM 5292 Colour Display Station Announced Brief Description of Announcement, Charges, and Availability (#ZG82-0275) [accessed 2023-01-21].. The 529X type Model F keyboard's physical layout arrangement for the most part is the same as its 525X-83 type Model B predecessor but is now shared with the IBM 532X System/23 Datamaster and early IBM Personal Computer keyboards. The 525X physical layout and the side-accessible adjustable feet are the defining differences between 529X and the 3101/3104/3178 keyboard platform. In terms of size, the 529X keyboard is smaller than Datamaster's but larger than the PC's and has three-setting adjustable feet that no other Model F keyboard has. Its bezel size and its feet give the 529X type its common nickname "bigfoot" in the keyboard community.

Background 2: changing times

The years following the Model F's introduction redefined much in how IBM terminals were numbered and how unified the keyboard designs became. Two new keyboard designs were quickly introduced and the IBM terminal numbering relationship for 3270 and 5250 was changed twice. In March 1983, IBM announced the 3270-compatible IBM 3290 Information Panel^[19][19]
IBM - IBM 3290 Information Panel Brief Description of Announcement, Charges, and Availability (#183-033) [accessed 2023-01-23]. that debuted the 104-key Model F (aka, "unsaver") keyboard that was the first IBM keyboard to introduce the 24-key single-unit function key bank many IBM terminal keyboards sported from then on. IBM called such keyboards Converged Keyboards. A few months later in October, IBM announced the IBM 3270 Personal Computer (type 5271)^[20][20]
IBM - IBM 3270 Personal Computer Brief Description of Announcement, Charges, and Availability (#186-117) [accessed 2023-01-23]. that debuted the 122-key Model F Converged Keyboard and its 122-key physical layout that's still in use today as-is. In March 1984, IBM announced the IBM 3179 Color Display Station^[21][21]
IBM - IBM 3179 Color Display Station Brief Description of Announcement, Charges, and Availability (#184-039) [accessed 2023-01-23]. and the IBM 3180 Display Station^[22][22]
IBM - IBM 3180 Display Station Models 1 and 2 Brief Description of Announcement, Charges, and Availability (#184-040) [accessed 2023-01-23]., which introduced the first change in terminal naming, where both terminals had a "Model 1" and "Model 2" that were 3270 compatible and 5250 compatible respectively despite the type number not changing.

By June 1986, IBM revised their terminal type numbering relationship for 3270 and 5250 again where all terminals released within a generation shared the same first three digits but the last digit determined family. The IBM 3191 and 3196 Display Stations were released first as the 3270 and 5250 offerings under this nomenclature respectively^[25][25]
IBM - IBM 3191 Display Station Brief Description of Announcement, Charges, and Availability (#186-117) [accessed 2023-01-23].^[26][26]
IBM - IBM 3196 Display Station Brief Description of Announcement, Charges, and Availability (#186-111) [accessed 2023-01-23].. From then on, terminals with a last digit less than 5 were 3270 and more than 5 were 5250. This nomenclature was retained when IBM introduced the InfoWindow branding, with the original InfoWindow (347X) in June 1989^[27][27]
IBM - IBM InfoWindow 3471 Display Station Brief Description of Announcement, Charges, and Availability (#189-096) [accessed 2023-01-23].^[28][28]
IBM - IBM InfoWindow 3476 Display Station Brief Description of Announcement, Charges, and Availability (#189-097) [accessed 2023-01-23]. and InfoWindow II (348X) in September 1992^[29][29]
IBM - IBM InfoWindow II 3486/3487 Display Station Brief Description of Announcement, Charges, and Availability (#192-192) [accessed 2023-01-23].^[30][30]
IBM - IBM InfoWindow II 3481/3482 Display Station Brief Description of Announcement, Charges, and Availability (#192-237) [accessed 2023-01-23]..

The IBM 3101 finally received follow-ups but their nomenclature remained separate. In June 1985, IBM announced the 316X family with 3161 and 3163 ASCII Display Stations at the same time they withdrew the IBM 3101 Model 230/881 from marketing^[32][32]
IBM - IBM 3161 and IBM 3163 ASCII Display Stations Models 11 and 12 Brief Description of Announcement, Charges, and Availability (#185-078) [accessed 2023-01-23].. In June 1987, IBM announced the 315X family with the 3151 ASCII Display Station^[33][33]
IBM - IBM 3151 ASCII Display Station Brief Description of Announcement, Charges, and Availability (#187-132) [accessed 2023-01-23].. Both are capable of 3101 (and various third-party terminals) emulation.

Other Model F & Model M keyboards

As described above, the late Model F era/early Model M era saw IBM introducing a lot of changes that ultimately saw IBM unify its terminal keyboards into three physical designs that could be shared by all three families and differed only in the functional layout (ie, what's written on the keycaps). Furthermore, several more nuances come into play, especially with the rise of PC-style terminal keyboards and terminal emulator (host-connected) keyboards. As such, a different approach to identification is needed. Typical keyboards include:

The terminal and terminal emulator versions of the Enhanced Keyboard and 122-key Model Ms are still in production via Unicomp.

You can identify these keyboards' family layout...

By part or model numbers

The most obvious first place to look for better identification of the keyboard is the back as IBM usually ensured (and Unicomp still ensures) that there was strong documentation on the back of the keyboard in the form of a rear label colloquially referred to as the keyboard's "birth certificate". Typically, the rear label sticker contains at least a part number, date of manufacturer, serial/ID number and country of manufacture. The contents and variety of these labels are demonstrated in the Keyboard Rear Labels topic.

You can check the part number against the Keyboard Part Number Database to find out what the host system might be. Typically, the title of an entry can reveal this, although a recently added datapoint to the database called "Known Host Systems" is currently being populated to cleanly list possible host systems for a given keyboard.

If a given keyboard happens to be made by IBM Netherlands, it may additionally have a "Type" field in the top right corner of the rear label clearly stating what machine the keyboard was designed for. However, other IBM factories and later OEMs seldom employed such a detailed sticker design. Instead, some terminal Model F and Model M keyboards may have auxiliary stickers that portrayed the host computer's type number. Unfortunately, these too are not universally common although many of such stickers may have just been lost over the years.

By navigation cluster layout

The keys positioned where the navigation keys (home, end, page up, page down) would be on consumer/PC keyboards are a great indicator of the keyboard's terminal family. Below are some general rules to follow when examining these 6-key clusters.

3101

3270

5250

By numeric keypad layout

Provided the keyboard in question has one, the numeric keypad can also be used for identifying the keyboard's terminal family. 3101, 3270 and 5250 helpfully all used different layouts beyond the simple 0 to 9 keys, shaped largely by trying to fit the layout of the Model B era keyboards into these newer layouts. However, there is variance within each family that has also been noted.

3101

3270

5250

Further reading & resources

Internal

Sources

ASK. Admiral Shark's Keyboards original content. License/note: CC BY-NC-SA 4.0.

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