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The Model M keyboard is a class of computer keyboards manufactured by IBM, Lexmark and finally Unicomp, starting in the 1980s.

The Model M was considered a class of keyboards rather than a specific model, as the many different models of the keyboard had their own distinct characteristics. Model Ms have been prized by computer enthusiasts and heavy typists, because most models included convenient fully swappable keycaps and a sturdy and reliable buckling spring key design. The Model M is also remembered for its overall heavy and sturdy design, which allowed the keyboard to survive far longer periods of time, use, and abuse than practically any other personal computer component ever manufactured.

Many Model Ms manufactured in the mid 1980s are still in use today (2006), while the computers and monitors of the day have long since been thrown out, recycled, or retired to museums.

History

Production for the original Model M began in 1984, and the keyboards were often bundled with new IBM computers in the 1980s. These keyboards were produced by IBM, made in the United States, and had part number 1391401. Until 1987, the keyboards featured a detachable AT cable; after that, they were bundled with a detachable PS/2 cable. Cables came in both 5 foot and 10 foot lengths.

In 1991, IBM divested a number of its hardware manufacturing operations to form Lexmark; the Model M keyboard group was subsequently sold to Lexmark in 1993. The Lexmark-produced keyboards are identifiable by the back label, which clearly says "Manufactured for IBM by Lexmark", and most had part number 42H1292. Widely regarded as somewhat inferior in build quality to the original Model M, the 42H1292 also featured internal drainage channels designed to minimize damage in case of a spill. These keyboards were produced until 1996.

After that, a company called Unicomp bought the Model M design from Lexmark. The design, the same as the 42H1292 design but renamed 42H1292U, is still in production (as of 2006). Different configurations can be purchased from Unicomp, including updated 104-key layouts, a "Linux" model (where the Ctrl and Caps Lock keys are swapped), models with integrated Trackpoint pointing sticks, and POS-specific models, such as those with built-in magstrip readers. Although current Unicomp models may be purchased for roughly 50 USD, original production models retain their value well among collectors as well as computer enthusiasts, and it is not uncommon to see them selling for upwards of 150 USD for a single, used unit.

There are numerous flavors of the Model M, but many of them are exceedingly rare. Sometimes it may be problematic to get them to communicate properly with a modern computer. A PS/2 to USB adapter would be necessary for computers without PS/2 ports, and the AT Model Ms additionally require an AT to PS/2 adapter. Some PS/2 to USB adapters are unreliable because the Model M tends to draw more power than some adapters expect. However, Unicomp has recently added USB models to their lineup.

Design

The model people commonly refer to when they mention "Model M" is Part No. 1391401, which was by far the most common. This enhanced keyboard model included the patented buckling spring design and swappable keycaps, as well as the heavy and sturdy design of the Model Ms in general. This keyboard is widely praised as being exceedingly well-built, and indeed one of the longest lived (and loudest) computer components ever made. Part of this can be attributed to the fact that keyboard design has changed little in the past twenty years, while the designs of everything from PCs to monitors to mice have changed dramatically. The sturdy design (including heavy steel backplates and a high-quality, strong plastic frame) of the keyboard allows even the most abused to survive these years with ease. The various models of the keyboard had small differences, while keeping the style of the key mechanism that makes the boards unique. The 1391472 model, for example, does not have a separate number pad, rather it incorporates a number pad into the body of the main keys as many laptop keyboards do. Likewise, the early 1390120 series did not feature LED indicators for the locking keys.

Most fans of the Model M especially prize its feel and sound. Unlike the common (but cheaper) dome switch design in use today, the Model M's buckling spring design gives users obvious tactile (a distinctive resistance as the keys are depressed) and aural (a characteristic, loud "click-clack"ing) feedback while typing, in ways similar to that of the keyboards of the long-running IBM Selectric typewriter line. In addition, the Model M keyboard is less susceptible to dirt and wear and tear; while dirt will interfere with proper operation of a dome switch keyboard, the design of a buckling spring keyboard is such that any dirt that falls between the cracks usually fails to make it into the spring mechanism. Failure of the mechanism to operate properly would require a large amount of accumulation, which is unlikely to occur.

There are some drawbacks to the Model M design, however. Because the keyboard is so heavy, it is not as portable as many modern keyboards. The keys are very noisy and would be inappropriate in a situation (such as a public library) where noise is an issue. Also, any liquids spilled on the keyboard would not drain out, and would remain in the keyboard with potential to cause a short circuit. The 42H1292 design and post-1993 1391401's, mostly made by Lexmark and Unicomp, includes drainage channels to prevent this, though it is done at the slight expense of the keyboard's quality.

Identification

All model M keyboards manufactured by either IBM or Lexmark feature an ID label indicating the individual serial number, the model designation, and the date the keyboard was minted. There are other more obvious ways to distinguish between the range, namely the type of badge featured on the top of the board. The first model M's (series 1390120 or 1390131) featured a square aluminium IBM badge in the top right corner. The next series (1391401) featured an oval, white IBM logo with grey lettering in the top left of the board. The later IBM manufactured boards and subsequent Lexmark boards of the early 90's (52G9658, 92G7453 or 42H1292) featured a similar oval badge to the 1391401, only with a grey background and blue lettering. Aside from these badging differences, the easiest way to distinguish between an IBM manufactured keyboard and a Lexmark or Unicomp board is the original IBM boards all feature a detachable cable.

Features by part number

Note: The manufacture dates are approximate.

See also

• Computer keyboard
• Buckling spring

References

• Review of the IBM 42H1292 and 1391401 keyboards by Dan's Data
• Clicky keyboards
• US patent 4118611, Richard Hunter Harris, "Buckling Spring Torsional Snap Actuator", issued 1978-10-03  — an IBM patent for buckling spring keys.

External links

• Modelm.org: A Model M Repository site (currently down)
• Care and feeding of an IBM Model M keyboard : A Model M restoration guide

• Computer keyboards
• IBM hardware