View source for 12-bit computing

{{Short description|Computer architectures using a 12-bit word}}
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{{N-bit|12|(1.5 octets)}}

Before the widespread adoption of [[ASCII]] in the late 1960s, [[six-bit character code]]s were common and a 12-bit word, which could hold two characters, was a convenient size. This also made it useful for storing a single decimal digit along with a sign. Possibly the best-known 12-bit CPUs are the [[PDP-8]] and its descendants (such as the [[Intersil 6100]] microprocessor), which were produced in various forms from August 1963 to mid-1990. Many [[Analog-to-digital converter|analog to digital converters]] (ADCs) have a 12-bit resolution. Some [[PIC microcontroller]]s use a 12-bit instruction word but handle only 8-bit data.

12 binary digits, or 3 nibbles (a 'tribble'), have 4096 (10000 [[octal]], 1000 [[hexadecimal]]) distinct combinations. Hence, a microprocessor with 12-bit memory addresses can directly access 4096 [[Word (computer architecture)|words]] (4&nbsp;kW) of [[word-addressable]] memory. IBM [[System/360]] instruction formats use a 12-bit displacement field which, added to the contents of a base register, can address 4096 bytes of memory in a region that begins at the address in the base register.

==List of 12-bit computer systems==
[[File:Living Computers - DEC PDP-8 (31826785627).jpg|thumb|[[Digital Equipment Corporation]] [[PDP-8]]e, a 12-bit minicomputer introduced in 1970]]

* [[Digital Equipment Corporation]]
** [[PDP-5]]
** [[PDP-8]]
*** [[DECmate]], a personal computer based on the Intersil 6100
** [[PDP-12]]
** [[PDP-14]]
* [[Ford EEC#EEC I and II|Ford EEC I]] automotive engine control unit
** [[Toshiba TLCS-12]] microprocessor<ref name="shmj-1973-toshiba">{{cite web |title=1973: 12-bit engine-control microprocessor (Toshiba) |url=http://www.shmj.or.jp/english/pdf/ic/exhibi739E.pdf |website=Semiconductor History Museum of Japan |access-date=27 June 2019}}</ref>
* [[Intersil]] [[Intersil 6100|IM6100]] microprocessor (PDP-8-compatible)
* [[Control Data Corporation]]
** [[CDC 160 series]] computers
** [[CDC 6600]] - Peripheral Processor (PP)
* [[National Cash Register]] [[NCR 315]]
* [[Scientific Data Systems]] SDS 92
* [[Nuclear Data, Inc.]] [[ND812]]
* [[PC12 minicomputer]]
* [[Ferranti Argus]]
* [[LINC]], later commercialized by DEC as the [[LINC-8]]

==See also==
* [[FAT12]], a file system with [[12-bit FAT cluster|12-bit wide cluster entries]]

==References==
{{Reflist}}

==External links==
* [https://gordonbell.azurewebsites.net/digital/timeline/12-bit.htm DIGITAL Computing Timeline: 12-bit architecture]
{{CPU technologies}}

[[Category:Computer data]]


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