12-bit computing
Computer architectures using a 12-bit word From Wikipedia, the free encyclopedia
In computer architecture, 12-bit integers, memory addresses, or other data units are those that are 12 bits (1.5 octets) wide. Also, 12-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size.
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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 CPU is the PDP-8 and its relatives, such as the Intersil 6100 microprocessor produced in various forms from August 1963 to mid-1990. Many analog to digital converters (ADCs) have a 12-bit resolution. Some PIC microcontrollers use a 12-bit word size.
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 words (4 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.
- Digital Equipment Corporation
- Ford EEC I automotive engine control unit
- Toshiba TLCS-12 microprocessor[1]
- Intersil 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
- Electronic Arrays 9002 (12-bit addressing but 8-bit byte)
- FAT12, a file system with 12-bit wide cluster entries
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