24-bit computing: Difference between revisions

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{{N-bit|24|(3 octets)}}

Notable '''24-bit''' machines include the [[CDC 924]] – a 24-bit version of the [[CDC 1604]], [[CDC 3000|CDC lower 3000 series]], [[SDS 930]] and [[SDS 940]], the [[ICT 1900 series]], the [[Elliott Brothers (computer company)|Elliott]] 4100 series, and the [[Datacraft Corporation|Datacraft]] minicomputers/[[Harris Computer Systems|Harris]] H series.<ref>{{cite web | url = http://www.quadibloc.com/comp/cp0303.htm | title = Real Machines with 24-bit and 48-bit words | access-date = 2011-02-11 | last = Savard | first = John| archive-url= https://web.archive.org/web/20110107183451/http://quadibloc.com/comp/cp0303.htm| archive-date= 7 January 2011 | url-status= live}}</ref>

The term SWORD is sometimes used to describe a 24-bit data type with the S prefix referring to [[wikt:sesqui|sesqui]].{{cn|date=October 2018}}

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== Usage ==

The IV/70, was introduced by [[Four-Phase Systems]] in 1971. The IV/70 has an integer word size of 24 bits. [[Byte]] addressing is not supported directly but bytes are handled by instructions that pack three bytes per word. The IV/70 CPU is a 9-chip [[Integrated_circuit#LSI|LSI]] [[microprocessor]] based on three [[Four-Phase Systems AL1|AL4]] 8-bit slice register/ALUs.<ref>[http://archive.computerhistory.org/resources/text/Four-Phase_Systems/Four-Phase.SystemIV_70.1970.102646129.pdf Brochure, System IV/70, Four Phase Systems]. From the Computer History Museum. Accessed online June 11, 2010.</ref>

The IBM [[System/360]], announced in 1964, was a popular computer system with 24-bit addressing and [[32-bit]] general registers and arithmetic. The early 1980s saw the first popular personal computers, including the [[IBM Personal Computer/AT|IBM PC/AT]] with an Intel [[80286]] processor using 24-bit addressing and [[16-bit computing|16-bit]] general registers and arithmetic, and the [[Apple Inc.|Apple]] [[Macintosh 128K]] with a Motorola [[68000]] processor featuring 24-bit addressing and 32-bit registers.

The IBM [[System/360]], announced in 1964, was a popular computer system with 24-bit addressing and [[32-bit]] general registers and arithmetic. The early 1980s saw the first popular personal computers, including the [[IBM Personal Computer/ AT|IBM PC/AT]] with an Intel [[Intel 80286]] processor using 24-bit addressing and [[16-bit computing|16-bit]] general registers and arithmetic, and the [[Apple Inc.|Apple]] [[Macintosh 128K]] with a Motorola [[Motorola 68000]] processor featuring 24-bit addressing and 32-bit registers. Some late-1980s Apple computers such as the [[Macintosh SE/30]] and [[Macintosh IIx]] retained some 24-bit code in their [[ROM image|ROMs]] despite being advertised as 32-bit computers. As a result, these computers require the installation of the [[MODE32]] memory manager to address more than 8Mb of RAM.<ref>{{Cite web |last=Staff |first=L. E. M. |date=1989-01-19 |title=Mac SE/30 |url=https://lowendmac.com/1989/mac-se30/ |access-date=2025-06-18 |website=Low End Mac |language=en-US}}</ref><ref>{{Cite web |last=Staff |first=L. E. M. |date=1988-09-19 |title=Mac IIx |url=https://lowendmac.com/1988/mac-iix/ |access-date=2025-06-18 |website=Low End Mac |language=en-US}}</ref>

The [[eZ80]] is a microprocessor and microcontroller family, with 24-bit registers and therefore 24-bit linear addressing, that is [[binary-code compatibility|binary compatible]] with the [[8-bit|8]]/16-bit [[Z80]]. {{cn|date=September 2015}}

The [[ARM1]], supported 24-bit memory address, as it can access 16MiB memory.

The [[eZ80]] is a microprocessor and microcontroller family, with 24-bit registers and therefore 24-bit linear addressing,. thatIt is [[binary-code compatibility|binary compatible]] with the [[8-bit|8]]/16-bit [[Z80]]. Although eZ80 supports 24-bit adds, subtracts, and moves, most ALU operations are limited to 8-bit.<ref>{{cncite book |title=eZ80 CPU User Manual |date=SeptemberJuly 15, 2009 |publisher=Zilog |edition=15, April 2015 |url=http://www.zilog.com/docs/um0077.pdf |access-date=16 June 2024}}</ref>

The [[65816]] is a microprocessor and microcontroller family with 16-bit registers and 24-bit [[bank switching|bank switched]] addressing. It is binary compatible with the [[8-bit]] [[6502]].<ref>{{cite magazine |author=Brett Tabke |url=http://www.defence-force.org/computing/oric/coding/annexe_2/ |title=A 6502 Programmer's Introduction to the 65816 |magazine=Commodore World magazine |issue=16 |year=1996}}</ref>