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 (such as the Intersil 6100 microprocessor), which were 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 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 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.

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 (such as the Intersil 6100 microprocessor), which were 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 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 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. ==List of 12-bit computer systems== PDP-8e, 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 I automotive engine control unit Toshiba TLCS-12 microprocessor 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 ==See also== FAT12, a file system with 12-bit wide cluster entries ==References== ==External links== DIGITAL Computing Timeline: 12-bit architecture

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