8-bit computing in the context of Bus (computing)

The IBM System/360 (S/360) is a family of computer systems announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applications and a complete range of sizes from small, entry-level machines to large mainframes. The design distinguished between architecture and implementation, allowing IBM to release a suite of compatible designs at different prices. All but the only partially compatible Model 44 and the most expensive systems use microcode to implement the instruction set, which used 8-bit byte addressing with fixed-point binary, fixed-point decimal and hexadecimal floating-point calculations. The System/360 family introduced IBM's Solid Logic Technology (SLT), which packed more transistors onto a circuit card, allowing more powerful but smaller computers, but did not include integrated circuits, which IBM considered too immature.

System/360's chief architect was Gene Amdahl and the project was managed by Fred Brooks, responsible to Chairman Thomas J. Watson Jr. The commercial release was piloted by another of Watson's lieutenants, John R. Opel, who managed the launch of IBM's System/360 mainframe family in 1964. The slowest System/360 model announced in 1964, the Model 30, could perform up to 34,500 instructions per second, with memory from 8 to 64 KB. High-performance models came later. The 1967 IBM System/360 Model 91 could execute up to 16.6 million instructions per second. The larger 360 models could have up to 8 MB of main memory, though that much memory was unusual; a large installation might have as little as 256 KB of main storage, but 512 KB, 768 KB or 1024 KB was more common. Up to 8 megabytes of slower (8 microsecond) Large Capacity Storage (LCS) was also available for some models.

The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit of memory in many computer architectures. To disambiguate arbitrarily sized bytes from the common 8-bit definition, network protocol documents such as the Internet Protocol (RFC 791) refer to an 8-bit byte as an octet. Those bits in an octet are usually counted with numbering from 0 to 7 or 7 to 0 depending on the bit endianness.

The size of the byte has historically been hardware-dependent and no definitive standards existed that mandated the size. Sizes from 1 to 48 bits have been used. The six-bit character code was an often-used implementation in early encoding systems, and computers using six-bit and nine-bit bytes were common in the 1960s. These systems often had memory words of 12, 18, 24, 30, 36, 48, or 60 bits, corresponding to 2, 3, 4, 5, 6, 8, or 10 six-bit bytes, and persisted, in legacy systems, into the twenty-first century. In this era, bit groupings in the instruction stream were often referred to as syllables or slab, before the term byte became common.

The W65C816S (also 65C816 or 65816) is a 16-bit microprocessor (MPU) developed and sold by the Western Design Center (WDC). Introduced in 1985, the W65C816S is an enhanced version of the WDC 65C02 8-bit MPU, itself a CMOS enhancement of the venerable MOS Technology 6502 NMOS MPU. The 65C816 is the CPU for the Apple IIGS and, in modified form, the Super Nintendo Entertainment System.

The 65 in the part's designation comes from its 65C02 compatibility mode, and the 816 signifies that the MPU has selectable 8- and 16-bit register sizes. In addition to the availability of 16-bit registers, the W65C816S extends memory addressing to 24 bits, supporting up to 16 megabytes of random-access memory. It has an enhanced instruction set and a 16-bit stack pointer, as well as several new electrical signals for improved system hardware management.

The ZX Spectrum (UK: /zɛd ɛks/) is an 8-bit home computer developed and marketed by Sinclair Research. The Spectrum played a pivotal role in the history of personal computers and video games, especially in the United Kingdom. It was one of the all-time bestselling British computers with over five million units sold. It was released in the UK on 23 April 1982, the United States in 1983, and Europe in 1984.

The machine was designed by the English entrepreneur and inventor Sir Clive Sinclair and his small team in Cambridge, and was manufactured in Dundee, Scotland by Timex Corporation. It was made to be small, simple, and most importantly inexpensive, with as few components as possible. The addendum "Spectrum" was chosen to highlight the machine's colour display, which differed from the black-and-white display of its predecessor, the ZX81. Rick Dickinson designed its distinctive case, rainbow motif, and rubber keyboard. Video output is transmitted to a television set rather than a dedicated monitor, while application software is loaded and saved onto compact audio cassettes.

A side-scrolling video game (alternatively side-scroller) is a video game viewed from a side-view camera angle where the screen follows the player as they move left or right. The jump from single-screen or flip-screen graphics to scrolling graphics during the golden age of arcade games was a pivotal leap in game design, comparable to the move to 3D graphics during the fifth generation.

Hardware support of smooth scrolling backgrounds is built into many arcade video games, some game consoles, and home computers. Examples include 8-bit systems like the Atari 8-bit computers and Nintendo Entertainment System, and 16-bit consoles, such as the Super Nintendo Entertainment System and Sega Genesis. These 16-bit consoles added multiple layers, which can be scrolled independently for a parallax scrolling effect.

The Apple Computer 1 (Apple-1), later known predominantly as the Apple I (written with a Roman numeral), is an 8-bit personal computer electrically designed by Steve Wozniak and released by the Apple Computer Company (now Apple Inc.) in 1976. The company was initially formed to sell the Apple I – its first product – and would later become the world's largest technology company. The idea of starting a company and selling the computer came from Wozniak's friend and Apple co-founder Steve Jobs.

The key differentiator of the Apple I was that it included video display terminal circuitry, allowing it to connect to a low-cost composite video monitor and keyboard instead of an expensive accompanying terminal such as the Teletype Model 33 commonly used by other early personal computers. The Apple I and the Sol-20 were some of the earliest home computers to have this capability.

x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. The 8086 was introduced in 1978 as a fully 16-bit extension of Intel's 8-bit 8080 microprocessor, with memory segmentation as a solution for addressing more memory than can be covered by a plain 16-bit address. The term "x86" came into being because the names of several successors to Intel's 8086 processor end in "86", including the 80186, 80286, 80386 and 80486. Colloquially, their names were "186", "286", "386" and "486".

The term is not synonymous with IBM PC compatibility, as this implies a multitude of other computer hardware. Embedded systems and general-purpose computers used x86 chips before the PC-compatible market started, some of them before the IBM PC (1981) debut.

The Intel 8080 is Intel's second 8-bit microprocessor. Introduced in April 1974, the 8080 was an enhanced non-binary compatible successor to the earlier Intel 8008 microprocessor. Originally intended for use in embedded systems such as calculators, cash registers, computer terminals, and industrial robots, its performance soon led to adoption in a broader range of systems, ultimately launching the microcomputer industry.

Several key design choices contributed to the 8080’s success. Its 40‑pin package simplified interfacing compared to the 8008’s 18‑pin design, enabling a more efficient data bus. The transition to NMOS technology provided faster transistor speeds than the 8008's PMOS, also making it TTL compatible. An expanded instruction set and a full 16-bit address bus allowed the 8080 to access up to 64 KB of memory, quadrupling the capacity of its predecessor. A broader selection of support chips further enhanced its functionality. Many of these improvements stemmed from customer feedback, as designer Federico Faggin and others at Intel heard from industry about shortcomings in the 8008 architecture.

The Commodore 64, also known as the C64, is an 8-bit home computer introduced in January 1982 by Commodore International (first shown at the Consumer Electronics Show, January 7–10, 1982, in Las Vegas). It has been listed in the Guinness World Records as the best-selling desktop computer model of all time, with independent estimates placing the number sold between 12.5 and 17 million units. Volume production started in early 1982, marketing in August for US$595 (equivalent to $1,940 in 2024). Preceded by the VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes (65,536 bytes) of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware.

The C64 dominated the low-end computer market (except in the UK, France and Japan, lasting only about six months in Japan) for most of the later years of the 1980s. For a substantial period (1983–1986), the C64 had between 30% and 40% share of the US market and two million units sold per year, outselling IBM PC compatibles, the Apple II, and Atari 8-bit computers. Sam Tramiel, a later Atari president and the son of Commodore's founder, said in a 1989 interview, "When I was at Commodore we were building 400,000 C64s a month for a couple of years." In the UK market, the C64 faced competition from the BBC Micro, the ZX Spectrum, and later the Amstrad CPC 464, but the C64 was still the second-most-popular computer in the UK after the ZX Spectrum. The Commodore 64 failed to make any impact in Japan, as their market was dominated by Japanese computers, such as the NEC PC-8801, Sharp X1, Fujitsu FM-7 and MSX, and in France, where the ZX Spectrum, Thomson MO5 and TO7, and Amstrad CPC 464 dominated the market.

The Atari Lynx is a fourth-generation handheld game console released by Atari Corporation in September 1989 in North America and 1990 in Europe and Japan. It was the first handheld game console with a color liquid-crystal display. Powered by a 4 MHz 65C02 8-bit CPU and a custom 16-bit blitter, the Lynx was more advanced than Nintendo's monochrome Game Boy, released five months earlier. It also competed with Sega's Game Gear and NEC's TurboExpress, released the following year.

The system was developed at Epyx by two former designers of the Amiga personal computers. The project was called the Handy Game or simply Handy. In 1991, Atari replaced the Lynx with a smaller model internally referred to as the Lynx II. Atari published a total of 73 games for the Lynx before it was discontinued in 1995.

The Zilog Z80 is an 8-bit microprocessor designed by Zilog, first released in 1976; it played an important role in the evolution of early personal computing. It was designed to be software-compatible with the Intel 8080, offering a compelling alternative due to its better integration and increased performance. Along with the 8080's seven registers and flags register, the Z80 introduced an alternate register set, two 16-bit index registers, and additional instructions, including bit manipulation and block copy/search.

Originally intended for use in embedded systems like the 8080 was, the Z80's combination of compatibility, affordability, and superior performance led to widespread adoption in video game systems and home computers throughout the late 1970s and early 1980s, helping to fuel the personal computing revolution. The Z80 was used in iconic products such as the Osborne 1, Radio Shack TRS-80, ColecoVision, ZX Spectrum, Sega's Master System and the Pac-Man arcade cabinet. In the early 1990s, it was used in portable devices, including the Game Gear and the TI-83 series of graphing calculators.