24-bit computing
Find sources: "24-bit computing" – news · newspapers · books · scholar · JSTOR (October 2009) (Learn how and when to remove this message)
| Computer architecture bit widths |
|---|
| Bit |
| Application |
| Binary floating-point precision |
| Decimal floating-point precision |
In computer architecture, 24-bit integers, memory addresses, or other data units are those that are 24 bits (3 octets) wide. Also, 24-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.
Notable 24-bit machines include the CDC 924 – a 24-bit version of the CDC 1604, CDC lower 3000 series, SDS 930 and SDS 940, the ICT 1900 series, the Elliott 4100 series, and the Datacraft minicomputers/Harris H series.[1]
The term SWORD is sometimes used to describe a 24-bit data type with the S prefix referring to sesqui.[citation needed ]
The range of unsigned integers that can be represented in 24 bits is 0 to 16,777,215 (FFFFFF16 in hexadecimal). The range of signed integers that can be represented in 24 bits is −8,388,608 to 8,388,607.
Usage
[edit ]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 LSI microprocessor based on three AL4 8-bit slice register/ALUs.[2]
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 PC/AT with an Intel 80286 processor using 24-bit addressing and 16-bit general registers and arithmetic, and the Apple Macintosh 128K with a 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 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.[3] [4]
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 24-bit linear addressing. It is binary compatible with the 8/16-bit Z80. Although eZ80 supports 24-bit adds, subtracts, and moves, most ALU operations are limited to 8-bit.[5]
The 65816 is a microprocessor and microcontroller family with 16-bit registers and 24-bit bank switched addressing. It is binary compatible with the 8-bit 6502.[6]
Several fixed-point digital signal processors have a 24-bit data bus, selected as the basic word length because it gave the system a reasonable precision for the processing audio (sound). In particular, the Motorola 56000 series has three parallel 24-bit data buses, one connected to each memory space: program memory, data memory X, and data memory Y.[7]
Engineering Research Associates (later merged into UNIVAC) designed a series of 24-bit drum memory machines including the Atlas, its commercial version the UNIVAC 1101, the ATHENA computer, the UNIVAC 1824 guidance computer, etc. Those designers selected a 24-bit word length because the Earth is roughly 40 million feet in diameter, and an intercontinental ballistic missile guidance computer needs to do the Earth-centered inertial navigation calculations to an accuracy of a few feet.[8] [failed verification ]
OpenCL has a built-in intrinsic for multiplication (mul24()) with two 24-bit integers, returning a 32-bit result. It is typically much faster than a 32-bit multiplication.[9]
See also
[edit ]- Catena, a term used for a 24-bit unit of data on the Bull Gamma 60 computer
References
[edit ]- ^ Savard, John. "Real Machines with 24-bit and 48-bit words". Archived from the original on 7 January 2011. Retrieved 2011年02月11日.
- ^ Brochure, System IV/70, Four Phase Systems. From the Computer History Museum. Accessed online June 11, 2010.
- ^ Staff, L. E. M. (1989年01月19日). "Mac SE/30". Low End Mac. Retrieved 2025年06月18日.
- ^ Staff, L. E. M. (1988年09月19日). "Mac IIx". Low End Mac. Retrieved 2025年06月18日.
- ^ eZ80 CPU User Manual (PDF) (15, April 2015 ed.). Zilog. July 15, 2009. Retrieved 16 June 2024.
- ^ Brett Tabke (1996). "A 6502 Programmer's Introduction to the 65816". Commodore World magazine. No. 16.
- ^ "24-BIT. DIGITAL SIGNAL PROCESSOR. FAMILY" (PDF).
- ^ "UNIVAC 24-bit computer genealogy".
- ^ "integerFunctions(3) Manual Page". www.khronos.org.