12-bit computing
Before the widespread adoption of ASCII in the late 1960s, six-bit character codes 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, which were produced in various forms from August 1963 to mid-1990. Many analog to digital converters have a 12-bit resolution. Some PIC microcontrollers use a 12-bit instruction word but handle only 8-bit data.
12 binary digits, or 3 nibbles, have 4096 distinct combinations. Hence, a microprocessor with 12-bit memory addresses can directly access 4096 words 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
- Digital Equipment Corporation
- * PDP-5
- * PDP-8
- ** DECmate, a personal computer based on the Intersil 6100
- * PDP-12
- * PDP-14
- Ford EEC I automotive engine control unit
- * Toshiba TLCS-12 microprocessor
- Intersil IM6100 microprocessor
- Control Data Corporation
- * CDC 160 series computers
- * CDC 6600 - Peripheral Processor
- 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