Also applies to Lexmark Quiet Touch Keyboard and Unicomp Mighty Mouse
- Updated 24 June 2023
The original IBM Space Saver series and later Unicomp Mighty Mouse series (codename "Surf") were low-profile (for the time) desktop peripherals introduced in 1992 and produced until 2010. These were the marketing names of the Models M4 and M4-1 IBM buckling rubber sleeve keyboards and numeric keypads, which in turn were desktop/general-purpose adaptations of the IBM Personal System/2 L40SX portable computer keyboard assembly and its Model M3 PS/2 L40SX Numeric Keypad respectively. These should not be confused with the earlier buckling spring based IBM Space Saving Keyboard (SSK). The Model M4 was simply an L40SX keyboard assembly inside a purpose-made case and attached to a PS/2 compatible controller, whereas the Model M4-1 adds a TrackPoint II pointing stick and two mouse buttons to the design. The numeric keypads were designated either M4 or M4-1 to match their host keyboard but didn't differ from each other. Models M4 and M4-1 were used for space-restricted environments (as the name suggests), energy-efficient computing, server monitoring, sysadmin and laptop docking solutions. The M4-1 keyboard in particular has the distinction of being the first IBM desktop keyboard with a TrackPoint pointing stick.
|Marketing names (keyboards)||IBM Quiet Touch Keyboard, IBM Space Saver Keyboard, IBM ThinkPad Space Saver Keyboard, Lexmark Quiet Touch Keyboard, Unicomp Mighty Mouse|
|Marketing names (numeric keypads)||IBM Space Saver Numeric Keypad, IBM Quiet Touch Numeric Keypad, Unicomp Mighty Mouse Num Pad, Unicomp Mighty Mouse Numeric Key Pad|
|OEM(s)||Lexmark, Key Tronic, Unicomp|
|Designation||M4 & M4-1|
|FCC ID(s)||IYL1397901 (Lexmark M4), IYL1397590 (Lexmark M4-1), CIGM4-1 (Key Tronic M4-1)|
|First appeared||2nd March 1992 (FCC final action date)
FCCID.io - Lexmark International Inc Keyboard 1397901 [accessed 2023-04-27].
Deskthority wiki - Unicomp Keyboards [accessed 2022-01-01].
|Switches||IBM buckling rubber sleeve (M3/M4/M4-1 rod-actuated variant)|
|Keycaps||Dye-sublimated (pearl white) or pad-printed (raven black) PBT|
|Case dimensions (keyboards)||33cm x 6cm x 3.8cm (12.99" x 2.36" x 1.5")|
|Case dimensions (numeric keypads)||9.2cm x 6cm x 3.8cm (3.62" x 2.36" x 1.5")|
|Case material||PC + ABS|
|Case colour(s)||Pearl white or raven black|
|Weight (keyboards)||~0.68kg (1.5lbs)
Unicomp - The Mighty Mouse Keyboard [accessed 2022-01-21].
|Weight (numeric keypads)||~0.23kg (0.5lbs)
Unicomp - The Mighty Mouse Keyboard [accessed 2022-01-21].
|Layout (keyboards)||84 (ANSI) or 85 (ISO) key compacted tenkeyless|
|Layout (numeric keypads)||17/18/19 key configurable at purchase|
|Connectivity (keyboards)||AT: 6-pin SDL to single PS/2 (M4) or dual PS/2 (M4-1) cable|
|Connectivity (numeric keypads)||Matrix passthrough: modular 10P10C to modular 10P10C cable|
|Notable features (keyboards)||TrackPoint II (M4-1 only), PS/2 mouse passthrough (M4-1 only)|
|Predecessor||IBM Space Saving Keyboard (indirect)|
|Successor||IBM Space Saver II|
The Model M4 family - both keyboard and keypad - design originated with the IBM PS/2 L40SX laptop's keyboard assembly and its numeric keypad option, which were originally released on 26th March 1991
IBM - THE IBM PS/2 MODEL L40 SX SYSTEM AND FEATURES [accessed 2022-06-14].. Development for the laptop started in February 1990, when IBM was already behind in the 386 laptop market. Looking to cut down development time for the machine, the buckling sleeves keyboard design skipped the usual mock-up and prototype stages and was quickly developed and pushed to production. IBM Information Products Corporation in Lexington, Kentucky under CEO Tom Hancock was responsible for the keyboard design
Computerworld - 1 April 1991 [accessed 2021-12-31].. Presumably, IBM decided to make a desktop version of its keyboard after the L40SX received good press for its keyboard
SharktasticA - Revealed: IBM Model M3 & M6 laptop buckling sleeves keyboards [accessed 2021-12-31].. After IBM Information Products Corporation had been spun off to form Lexmark International
SharktasticA - IBM Information Products Corporation [accessed 2021-12-31]., the new company patented the Model M4 design on 10th December 1991 with Thomas E. Pangburn listed as the inventor
Lexmark International Inc - Keyboard [accessed 2022-04-27]..
The earliest year of manufacture for an M4 observed is 1992
ASK Keyboard Archive Photos - P/N 1398051 (1992, Lexmark) [accessed 2022-01-08].. It started appearing in media by February 1992, with PC Mag praising the keyboard by saying "Most rubber-dome keyboards have a rubbery feel, but IBM/Lexmark's Quiet Touch Keyboard (not reviewed here), which is based on the keyboard of IBM's PS/2 L40SX, has as snappy a touch as you could wish for"
PC Mag - 1992-02-25 [accessed 2022-10-07].. In June 1993, the Model M4-1 became the default bundled keyboard for the IBM Personal System/2 E, the first Energy Star-compliant PC
IBM - IBM PS/2 E (9533), PS/2 14" Energy Saver Color Monitor and IBM 9507 Color Display [accessed 2022-02-13].. Lexmark produced all M4s between 1992 and sometime between Q4 1995 and Q2 1996 and even marketed their own branded versions. In April 1996, Lexmark exited the keyboard market and all immediate production was transferred to Key Tronic. In 1998, Unicomp subsequently took over production and by the turn of the millennium had introduced their own branded version called the Mighty Mouse
Unicomp - Unicomp Product Catalog (2000) [accessed 2021-13-31]..
However, Unicomp continued to produce M4s for IBM until at least 2002
Geekhack - Re: Unusual mini Unicomp Model M (98U0176), $24.99+shipping [accessed 2021-12-31].. IBM M4s produced by Unicomp can be identified easily by the lock-light overlay style, which now uses Unicomp's signature lock icons instead of text. The Unicomp Mighty Mouse was ultimately retired in 2010. One unusual fact regarding Unicomp-made pointing stick Mighty Mouse keyboards was that Unicomp kept using a strain gauge TrackPoint II pointing stick instead of turning to their FSR stick design
Deskthority wiki - Unicomp Keyboards [accessed 2022-01-01]..
All inflation adjustments were made with US Inflation Calculator.
More information: IBM buckling rubber sleeve
The Model M4 and M4-1 keyboards were the first discrete (ie, not integrated into a laptop) keyboard to feature IBM buckling rubber sleeve (known simply as [IBM] buckling sleeves) key-switches, once IBM's primary portable computer and point-of-sale key-switch technology. The numeric keypads were beaten to their equivalent honour by the Model M3 L40SX Numeric Keypad. Unlike generic rubber dome key-switches, the rubber component in buckling sleeves plays no part in pressing down on the membrane assembly. Instead, the design offloads this duty to rods on the keycaps or barrel-mounted sliders (depending on specific implementation) that descend through the keyboard's key-switch barrels. This effectively eliminates the mushy feeling of bottoming out on rubber dome keyboards since the actuation interface is more solid, whilst still keeping the design tactile and relatively quiet. IBM buckling sleeves are very snappy and quite tactile with what's perhaps best described as a medium stiffness feel relative to other key-switch designs.
Models M4 and M4-1 use the same implementation of IBM buckling sleeves as M3, which is expected given that M4 keyboard assemblies originated on the IBM PS/2 L40SX. This means they use rod-actuated buckling sleeves where a fixed plunger on the keycap descends through the switch barrels to actuate the membrane underneath, giving a firm and solid bottom-out feel. Through the 18 years of production, the basic key-switch design remained unchanged although the colour and apparent thickness of the sleeves themselves could vary from one example of an M4 or M4-1 to another. The OEM, year of manufacture and colour of the outer casing seem to contribute to this. But, these differences shouldn't significantly alter the key feel or sound more than other factors such as wear and condition.
The Models M4 and M4-1 overall emulate the classic wedge shape of their larger buckling spring brethren and this profile was shared between keyboard and numeric keypad companion to maintain consistency. That said, the top profile is much flatter and more compact than most Model Ms before them and most closely resembles the Models M1 and M2 Selectric Touch Keyboards. The case is made of a PC and ABS copolymer and pearl white keyboards and numeric keypads can yellow, though by how much differs between the OEMs.
Unique to Model M4 keyboard
The Model M4 keyboard's case differs from the M4-1's by the lack of cut-outs for the M4-1's TrackPoint mouse buttons and PS/2 mouse passthrough port. Inside at least Lexmark-made M4s, the bottom case piece also has additional plastic support around the M4's smaller controller card.
Unique to Model M4-1 keyboard
Model M4-1 keyboard's case is the opposite of what's unique about the M4's case. There are cut-outs for their TrackPoint mouse buttons and PS/2 mouse passthrough port including a semi-circular cut-out on the keyboard's back-facing lip wall.
The internal keyboard and numeric keypad assembles themselves - again heavily related to the L40SX's M3-based keyboard and M3 numeric keypad respectively - somewhat resemble that of their larger Model M brethren, especially the keypads. The assemblies are comprised of three layers; the barrel plate and actuators, the membrane assembly, and the backplate.
- The barrel plate sits top facing and is used to guide the individual key-switch components (the buckling sleeve rubber elements) to their correct positions above the membrane assembly's contact points. In Unicomp's terminology, this is referred to as a "frame". The barrel plate design has a degree of redundancy in the number of barrels available, allowing for a 'one size fit all' design for ANSI or ISO (keyboard) and 17, 18 or 19 key (keypad) physical layouts.
- The membrane assembly is a part of the key-switch system used as the circuitry to be actuated and facilitates a 19x9 (keyboard) or 5x5 (keypad) matrix.
- The backplate provides some rigidity.
The keyboards and keypads however differ in how the assembly is held together. The keyboard assemblies use hooks from the backplate that attaches to the barrel plate, allowing the assembly to be opened non-destructively. The keypad assemblies are held together with melted plastic rivets infamously used with common Model M variants. These rivets are a possible failure point for Model M; if rivets break (especially in a localised area), the resulting loss of tension can at first cause faulty key registering. Such an issue could be permanently solved with a bolt or screw mod on a buckling spring or Quiet Touch rubber dome Model M - whilst the procedure hasn't been documented on an M4/M4-1 numeric keypad, it should be technically possible.
Models M4 and M4-1 can have two types of keycaps depending on the overall colour of the keyboard. If the keyboard/keypad is pearl white, it will have PBT keycaps with dye-sublimated legends. Versus the most common keycap material, ABS
WASD Keyboards - Mechanical Keyboard Guide [accessed 2021-09-09]., PBT is more durable, doesn't degrade/yellow with age, UV or heat exposure, and will keep its texture for longer without shining
Switch And Click - ABS vs PBT Keycaps: What’s the Difference? [accessed 2021-09-09].. Dye-sublimation is also a very durable text printing method that sinks dye material into the keycap's plastic itself, meaning there is nothing to quickly wear off as would be the case with pad-printing, silk screening, laser etching or laser etching with infill. But if the keyboard/keypad is raven black, however, it will have PBT keycaps with pad-printed legends instead. This is due to the fact one cannot sublimate dye that is lighter than the host plastic itself without inverse dyeing (ie, light host plastic and dye around where the text should be), which would have been more costly and this procedure is a relatively modern invention for keycap production. Pad-printed legends are perishable and there's no readily available replacement for M4 keycaps.
Models M4 and M4-1 share the same keycap mount as M3, which uses two clips on opposite edges of the keycap to retain it in place and prevent it from significantly rotating in its place. This keycap mount has not been observed on any other keyboard.
Models M4 and M4-1 keyboards use a controller card conceptually very similar to buckling spring Model Ms before their fourth generation revision that saw them move to a pressure fit controller. M4 controllers used the same 2.54mm pitch Triomate type connectors from TE Connectivity as first to third-generation full-size Model Ms for socketing the membrane assembly's flex cables and the lock-light LED daughterboard. The number of sockets varied between M4 and M4-1 and was reduced over time:
- Lexmark era (~1996) M4 controllers have three Triomates; 19-pin matrix connection, 9-pin matrix connection and 4-pin LED lock-lights connection
- Lexmark era (~1995) M4-1 controllers have four Triomates; 19-pin matrix connection, 9-pin matrix connection, 4-pin LED lock-lights connection and 4-pin mouse buttons connection
- Unicomp era (~1999) M4-1 controllers have two Triomates; a 22-pin combined matrix and mouse buttons connection and a 13-pin combined matrix and LED lock-lights connection
On the bottom of the keyboard in the top-left corner, the lock-light LED daughterboard can be found inside its own compartment and usually has some padding stuck to it. This connects via a 4-pin flex cable which can be a separate cable or integrated with a matrix connection cable as indicated above.
Models M4 and M4-1 numeric keypads lack a controller of any sort, instead, the internal PCB it does have simply transfers the membrane flex cable traces into the modular 10P10C socket's pins so that the host keyboard can sense keystrokes from the keypad. The membrane flex cable sockets used are still 2.54mm pitch Triomate type connectors from TE Connectivity albeit smaller. A single jumper is present that can bridge the last membrane trace of the second Triomate socket with a fill connected to the 101P10C socket's shield - its purpose is presently unknown.
Key Tronic OEM DIP switches
Key Tronic OEM Model M4-1 keyboards have a 4-position DIP switch on the back that's accessible through a small rectangular cut-out added to the moulds after all Lexmark production. The combination is set from the factory to tell the keyboard what functional layout the numeric keypad should have. This resulted in 5 very similar keyboards being available with different part numbers but the same FRU number to indicate what keyboards are preset with what switch positions. Despite that, any keyboard could be made to function like its 4 siblings but changing the switch combinations. Usually, the DIP switch bank is covered with a square white sticker. Rear labels on such keyboards indicate the following combinations:
SP = switch position.
Unicomp OEM configuration key codes
At some point, Unicomp implemented firmware-level numeric keypad layout configuration to replace the use of DIP switches. It is unclear when support was added and whether it affected just Unicomp self-branded keyboards or IBM-branded ones too, but those that do could support the following process:
- Press and hold Left Shift + Alt + Ctrl + F12 keys
- Release said keys
- Enter a two-digit code seen above that matches the numeric keypad's layout connected to the host keyboard
- Press and hold Right Shift + Alt + Ctrl
- Release said keys
Unicomp - Keypad Configuration for the Quiet Touch Keyboard [accessed 2023-04-27]. License/note: retrieved via Wayback Machine (2005-05-12 capture).
All M4-1 keyboards regardless of OEM or brand made use of IBM's TrackPoint II pointing stick featuring strain gauge sensors. This includes Unicomp-made M4-1s, which is something unusual since their other own-brand pointing stick keyboards (ie, Unicomp On-The-Stick and EnduraPro) used an alternative technology - force-sensing resistor (FSR) pointing sticks. This is the same stick found on Model M6 and early M6-1 based IBM ThinkPad keyboards and IBM-branded Model M13s. TrackPoint II lacks the negative inertia transfer function feature of the later TrackPoint III and IV revisions (the latter of which is still used by Lenovo today), meaning its performance can be less than ideal on modern high-resolution displays, but it's generally an accurate stick and contrasts well against alternatives of the period and Lexmark-Unicomp FSR pointing sticks found on Lexmark or Unicomp brand M13s or all Unicomp EnduraPros. The performance of the stick can be boosted on modern systems via software solutions such as interception drivers.
The Models M4 and M4-1 feature flip-out feet somewhat reminiscent of the Model M1/M2 foot. Typically, the feet also have some rubber padding on the bottom to help give them a bit more purchase and stop them from grinding down or scratching the host surface as easily. M4s have also been observed without this padding but it's unclear if this is due to wear, user removal, specific RPQ orders or OEM/factory/timeframe-specific nuances.
IBM-branded Model M4 and M4-1 keyboards used a mixture of oval badge branding over the years that could differ depending on whether it was an M4 or M4-1, what colour the rest of the keyboard was and even OEM. M4/M4-1 numeric keypads do not feature any branding besides what's written on their rear labels. The general rule of thumb on oval badge styling:
- Lexmark-made pearl white M4s used flat blue IBM text on grey background
- Lexmark-made pearl white M4-1s used raised grey IBM text on grey background
- Lexmark-made raven black M4-1s used raised blue IBM text on black background
- Key Tronic-made pearl white M4-1s used raised silver IBM text on grey background (however, this could wear off into simple grey text)
- Unicomp-made pearl white M4-1s used raised silver IBM text on grey background
- Unicomp-made raven black M4-1s used flat blue IBM text on black background
SharktasticA - Revealed: The Story of the Model M4 family [accessed 2022-01-02].
Lexmark's own-brand M4s had their usual rectangle logo in place of the oval badge whereas Unicomp's own-brand M4s retained the oval badge but had it blanked out with their branding on the lock-light overlay sticker itself.
As such, the lock-light overlay sticker was also subject to some variance depending on colour or brand. Pearl white and raven black Lexmark and Key Tronic OEM M4s used the same three-segment lock-light overlay, just with a different two-tone colour scheme to match the host keyboard's colour. Unicomp OEM M4s regardless of IBM or Unicomp branding used their signature symbols overlay style (without or with "Unicomp" branding respectively).
All Model M4 and M4-1 keyboards are AT-compatible and have modular cables, typically a 2.5-metre
Unicomp - The Mighty Mouse 84 Key [accessed 2021-12-31]. 6-pin SDL to PS/2 mini-DIN cable. As such, they're fully compatible with the SDL-based cables buckling spring Model Ms use and you could use a full-DIN AT cable with them if you so desired. M4-1s require a Y-split style dual PS/2 cable, however, single-plug PS/2 or AT DIN cables will still work albeit with no pointing device functionality.
Besides the SDL jack, all M4 and M4-1 keyboards also have a modular 10P10C jack for connecting a numeric keypad to the keyboard (see below for more information). This socket resembles an ethernet or RJ-45 socket but has 2 extra pins (the same socket used for RJ-50 applications).
All Model M4 and M4-1 numeric keypads likewise have a modular 10P10C jack. M4/M4-1 keypads are passive devices without any control electronics inside, so this 10-pin connection allows the keyboard to access the keypad's entire membrane matrix to perform keystroke sensing. This ultimately means that M4/M4-1 keypads cannot be used by themselves without making your own controller to either replace the keypad's internal PCB or connect to it via the modular 10P10C jack. A 1-metre 10P10C to 10P10C cable was normally included with the numeric keypad
IBM - IBM Quiet Touch Keyboard with Trackpoint II, IBM Quiet Touch Numeric Keypad and IBM Enhanced Mouse Brief Description of Announcement, Charges, and Availability [accessed 2022-02-02]..
The Model M4 keyboard proper was a straight adaptation of the Model M3-based IBM PS/2 L40SX keyboard assembly albeit in its own case and sporting a PS/2-compatible controller and LED lock-lights. IBM-branded and Lexmark-branded examples have so far only been observed in pearl white (IBM's trade name for off-white colour), thus since they're made from PC + ABS, it is possible for them to visibly yellow. Unicomp later made self-branded raven black (IBM's trade name for black colour) keyboards. M4s seem to be far less common than M4-1s - it's unclear if they indeed sold less during their heyday or if they were simply discarded more often since they lack the novelty of a TrackPoint pointing stick.
The Model M4-1 keyboard was the more iconic variant of the family, being largely the same as the M4 but sporting a TrackPoint II pointing stick and two mouse buttons. IBM-branded M4-1s can also be found in raven black as well as pearl white, giving them a resemblance to ThinkPad portable computer keyboards such as their close cousins of the Model M6 family. Indeed, M4-1 part numbers can often be found in many 1990s ThinkPad hardware maintenance manuals as an accessory option. Black M4-1s also lack dye-sublimated keycaps, meaning their key legends can wear off.
The Models M4 and M4-1 numeric keypads were the companions for the M4 family keyboards. Whilst they could have either M4 and M4-1 designations, the numeric keypads didn't differ mechanically and electrically and simply received a designation to match the host keyboard the keypad was purchased with. As demonstrated in the Numeric keypad layout configuration section, the numeric keypads could have up to five (at least during the Key Tronic OEM era) or six (at some point during the Unicomp era) configurations. These configurations used one of the three following physical layouts:
- 17-key Model M4/M4-1 numeric keypads use the same layout as their M3 cousins. It's the standard numeric keypad layout that's still in use today.
- 18-key Model M4/M4-1 numeric keypads typically gain the extra key from splitting the 2-unit 0 key into two 1-unit keys "0" and "00". The addition of a "00" key is useful for adding machines and cash registers
Wikipedia - Numeric keypad [accessed 2022-01-10]..
- 19-key Model M4/M4-1 numeric keypads also split the 2-unit 0 key into two 1-unit keys "0" and "00", but they also gain another key from splitting the 2-unit + key. The functionality is subject to variance for their right-most column. Presently, two distinct variations are known; 1u -, 1u +, 1u Enter and 2u Tab (as pictured), or 1u -, 1u +, 1u End and 2u Enter.
Part number list
71 part numbers have been found in the ASK Keyboard Part Number Database. If you believe a relevant part number is missing, you can help improve this list by requesting a submission for it to be added.
- P/N 02U0206: Unicomp Mighty Mouse Num Pad
- P/N 1379044 (FRU 8259635): IBM Space Saver Numeric Keypad
- P/N 1379550 (FRU 61G2903): IBM Space Saver Numeric Keypad
- P/N 1379590 (FRU 61G2901): IBM Space Saver Keyboard
- P/N 1379593 (FRU 61G2837): IBM Space Saver Keyboard
- P/N 1379595 (FRU 61G2845): IBM Space Saver Keyboard
- P/N 1397451 (FRU 1397470): IBM Space Saver Keyboard
- P/N 1397461 (FRU 1397480): IBM Space Saver Numeric Keypad
- P/N 1397901: Lexmark Space Saver Keyboard
- P/N 1398051 (FRU 1398053): IBM Space Saver Numeric Keypad
- P/N 28L3640 (FRU 84G2529): IBM 84-Key Space Saver Keyboard with TrackPoint
- P/N 28L3641 (FRU 84G6297): IBM 84-Key Space Saver Keyboard with TrackPoint
- P/N 28L3642 (FRU 84G6285): IBM 84-Key Space Saver Keyboard with TrackPoint
- P/N 28L3643 (FRU 84G6279): IBM 84-Key Space Saver Keyboard with TrackPoint
- P/N 61G2841: IBM Space Saver Keyboard
- P/N 61G2849: IBM Space Saver Keyboard
- P/N 61G2853: IBM Space Saver Keyboard
- P/N 61G2857: IBM Space Saver Keyboard
- P/N 61G2861: IBM Space Saver Keyboard
- P/N 61G2865: IBM Space Saver Keyboard
- P/N 61G2869: IBM Space Saver Keyboard
- P/N 61G2873: IBM Space Saver Keyboard
- P/N 61G2877: IBM Space Saver Keyboard
- P/N 61G2881: IBM Space Saver Keyboard
- P/N 61G2885: IBM Space Saver Keyboard
- P/N 61G2889: IBM Space Saver Keyboard
- P/N 61G2893: IBM Space Saver Keyboard
- P/N 61G2897: IBM Space Saver Keyboard
- P/N 61G2905: IBM Space Saver Keyboard
- P/N 61G2909: IBM Space Saver Keyboard
- P/N 73G8306 (FRU 61G2901): IBM Quiet Touch Keyboard with TrackPoint II (9035)
- P/N 73G9775 (FRU 61G2903): IBM Quiet Touch Numeric Keypad (9131)
- P/N 82G3257: IBM Space Saver Keyboard
- P/N 82G3259: IBM Space Saver Keyboard
- P/N 82G3261: IBM Space Saver Keyboard
- P/N 82G3263: IBM Space Saver Keyboard
- P/N 82G3265: IBM Space Saver Keyboard
- P/N 82G3267: IBM Space Saver Keyboard
- P/N 82G3269: IBM Space Saver Keyboard
- P/N 82G3271: IBM Space Saver Keyboard
- P/N 82G3273: IBM Space Saver Keyboard
- P/N 82G3277: IBM Space Saver Keyboard
- P/N 84G2524 (FRU 84G2529): IBM Space Saver Keyboard
- P/N 84G2525 (FRU 84G2529): IBM Space Saver Keyboard
- P/N 84G2526 (FRU 84G2530): IBM Space Saver Numeric Keypad
- P/N 84G2529: IBM Space Saver Keyboard
- P/N 84G6279: IBM Space Saver Keyboard
- P/N 84G6280: IBM Space Saver Numeric Keypad
- P/N 84G6285: IBM Space Saver Keyboard
- P/N 84G6286: IBM Space Saver Numeric Keypad
- P/N 84G6288 (FRU 84G6291): IBM Space Saver Keyboard
- P/N 84G6292: IBM Space Saver Numeric Keypad
- P/N 84G6294 (FRU 84G6297): IBM Space Saver Keyboard
- P/N 84G6298: IBM Space Saver Numeric Keypad
- P/N 84G6303: IBM Space Saver Keyboard
- P/N 84G6304: IBM Space Saver Numeric Keypad
- P/N 84G6306 (FRU 84G6309): IBM Space Saver Keyboard
- P/N 84G6310: IBM Space Saver Numeric Keypad
- P/N 84G8525 (FRU 84G8567): IBM Space Saver Numeric Keypad
- P/N 84H8468 (FRU 84H8566): IBM Quiet Touch Keyboard with TrackPoint II
- P/N 84H8469 (FRU 84H8566): IBM Quiet Touch Keyboard with TrackPoint II
- P/N 84H8470 (FRU 84H8566): IBM Quiet Touch Keyboard with TrackPoint II
- P/N 84H8471 (FRU 84H8566): IBM Quiet Touch Keyboard with TrackPoint II
- P/N 84H8503 (FRU 84H8566): IBM Quiet Touch Keyboard with TrackPoint II
- P/N 84H8525 (FRU 84H8567): IBM Quiet Touch Numeric Keypad (E04024US)
- P/N 98U0150 (FRU 98U0150): Unicomp Mighty Mouse
- P/N 98U0151: Unicomp Mighty Mouse Num Pad
- P/N 98U0153: Unicomp Mighty Mouse
- P/N 98U0154: Unicomp Mighty Mouse Num Pad
- P/N 98U0176: Unicomp Mighty Mouse
- P/N U2B04A2: Unicomp Mighty Mouse
More information: TrackPoint, pointing stick, and UltraNav keyboards#RT3200
The Model M4 family was directly succeeded by the NMB-made IBM Space Saver II, which was introduced in 1999. Better known by its model number RT3200, the Space Saver II was a full-travel rubber dome over membrane keyboard that featured a more conventional tenkeyless layout with Windows keys and larger modifiers and an SSK-style overlay numeric keypad. The Space Saver II could only be had with a TrackPoint stick and in black. However, the stick is now a TrackPoint IV revision that was far more performant than the M4-1's TrackPoint II stick due to the inclusion of a negative inertia transfer function in its firmware. The design also received a third mouse button.
- FCCID.io - Lexmark International Inc Keyboard 1397901 [accessed 2023-04-27].
- Deskthority wiki - Unicomp Keyboards [accessed 2022-01-01].
- Unicomp - The Mighty Mouse Keyboard [accessed 2022-01-21].
- IBM - THE IBM PS/2 MODEL L40 SX SYSTEM AND FEATURES [accessed 2022-06-14].
- Computerworld - 1 April 1991 [accessed 2021-12-31].
- SharktasticA - Revealed: IBM Model M3 & M6 laptop buckling sleeves keyboards [accessed 2021-12-31].
- SharktasticA - IBM Information Products Corporation [accessed 2021-12-31].
- Lexmark International Inc - Keyboard [accessed 2022-04-27].
- ASK Keyboard Archive Photos - P/N 1398051 (1992, Lexmark) [accessed 2022-01-08].
- PC Mag - 1992-02-25 [accessed 2022-10-07].
- IBM - IBM PS/2 E (9533), PS/2 14" Energy Saver Color Monitor and IBM 9507 Color Display [accessed 2022-02-13].
- Unicomp - Unicomp Product Catalog (2000) [accessed 2021-13-31].
- Unicomp - The Mighty Mouse 84 Key [accessed 2021-12-31].
- Geekhack - Re: Unusual mini Unicomp Model M (98U0176), $24.99+shipping [accessed 2021-12-31].
- IBM - IBM Quiet Touch Keyboard with Trackpoint II, IBM Quiet Touch Numeric Keypad and IBM Enhanced Mouse Brief Description of Announcement, Charges, and Availability [accessed 2022-02-02].
- Unicomp - Unicomp Keyboards [accessed 2022-01-02].
- Unicomp - Mighty Mouse - "Pearl White" [accessed 2022-02-02]. License/note: retrieved via Wayback Machine (1999-11-08 capture).
- Ripster - Ripster Keyboards - IBM M4 [accessed 2023-04-25]. License/note: used under fair dealing.
- WASD Keyboards - Mechanical Keyboard Guide [accessed 2021-09-09].
- Switch And Click - ABS vs PBT Keycaps: What’s the Difference? [accessed 2021-09-09].
- Unicomp - Keypad Configuration for the Quiet Touch Keyboard [accessed 2023-04-27]. License/note: retrieved via Wayback Machine (2005-05-12 capture).
- Brandon @ ClickyKeyboards - 1997 IBM model M4-1 keyboard with trackpoint (84H8470) 18-JUL-1997 and external numpad (84H8537) + spare keyboard assembly [accessed 2022-08-20].
- SharktasticA - Revealed: The Story of the Model M4 family [accessed 2022-01-02].
- Brandon @ ClickyKeyboards - photo used under permission.
- Wikipedia - Numeric keypad [accessed 2022-01-10].
|2023-06-24||Revisions for Model M4 & M4-1 Space Saver Keyboard & Numeric Keypad wiki page have been published - Fix "tenkeyle" -> "tenkeyless"|
|2023-05-08||Revisions for Model M4 & M4-1 Space Saver Keyboard wiki page have been published - Merge M4/M4-1 numpad page with this|
|2023-04-27||Revisions for Model M4 & M4-1 Space Saver Keyboard wiki page have been published - Add FCC IDs to "Summary", rewrote "Outer case" & added "Numeric keypad layout configuration"|
|2023-04-25||Revisions for Model M4 & M4-1 Space Saver Keyboard wiki page have been published - Add photo of Lexmark M4 controller under "Controller" and pearl white M4-1 under "Model M4-1"|
|2023-04-19||Revisions for Model M4 & M4-1 Space Saver Keyboard wiki page have been published - Add part number list section|
|2022-12-30||Revisions for Model M4 & M4-1 Space Saver Keyboard wiki page have been published - Change thumbnail from JPG to PNG|