RCA 1802
The COSMAC is an 8-bit microprocessor family introduced by RCA. It is historically notable as the first CMOS microprocessor. The first production model was the two-chip CDP1801R and CDP1801U, which were later combined into the single-chip CDP1802. The 1802 represented the majority of COSMAC production, and today the entire line is known simply as the RCA 1802.
The processor design traces its history to an experimental home computer designed by Joseph Weisbecker in the early 1970s, built at his home using TTL components. RCA began development of the CMOS version of the processor design in 1973, sampling it in 1974 with plans to move to a single-chip implementation immediately. Jerry Herzog led the design of the single-chip version, which sampled in 1975 and entered production in 1976.
In contrast to most designs of the era, which were fabricated using the NMOS process, the COSMAC was implemented in CMOS form and used static logic. This allowed it to run at lower power settings and even be stopped completely; in addition it would run cooler and not generate as much heat as NMOS chips. RCA also produced radiation hardened versions, which found use in the aerospace field. These remain in production as of 2022, and as of 2008 continued to be produced by Renesas.
Successors to the 1802 are the CDP1804, CDP1805, and CDP1806, which have an extended instruction set, other enhanced features, with some versions running at faster clock speeds, though not a significant speed difference. Some features are also lost, like the DMA auto-boot loader functionality. There are also some minor pin function changes, but as of 2026 the line continues to be produced in its original 40-pin dual in-line package format.
History
FRED
had long been fascinated with the potential for computers in the home, having stated as early as 1955 that he expected they would one day be built into practically every device. The technology of the era made small embedded computers impossible, but the introduction of the integrated circuit in the 1960s changed things dramatically. In 1974 he described the possibilities in an IEEE Computer article:Beginning in 1970, Weisbecker began the design of a small machine using RCA transistor-transistor logic ICs to construct the processor. Other parts, switches and lamps and such, he had to buy from Radio Shack, deliberately spreading his purchases around four stores so no one would ask him why he was buying so many parts. The design was running in October 1971, containing 100 chips spread over multiple circuit boards.
The result, which he called FRED, ostensibly for Flexible Recreational Educational Device, was packaged into a box that was not unlike the Altair 8800 of a few years later, with toggle switches on the front panel for input, lamps for output, and later adding a hex pad keyboard. Weisbecker added new features continually and by 1972 it had gained a character generator and the ability to load and save programs on cassette tapes.
Weisbecker's daughter, Joyce Weisbecker, was immediately drawn to the system and began writing programs for it. This included several games, which were ported to later machines based on the COSMAC. When RCA entered the game console business in the later 1970s, these games were burned to ROM cartridge form, and Joyce became the first known female commercial videogame developer.
Release
Weisbecker demonstrated the machine to RCA management throughout this period, but there was little interest at first. This was shortly after David Sarnoff had retired and handed the CEO role to his son, Robert Sarnoff. Robert was more interested in building the media side of the company while dating recording stars, ignoring RCA Laboratories in spite of a number of industry-leading developments taking place there. Some of the skepticism displayed by management may have had to do with the company's recent sale of their mainframe computer business to Sperry Rand with a huge writedown.Eventually, the company became interested in the system and began adapting it to their newly introduced COS/MOS fabrication system. A 1973 lab report refers to a "prototype" being delivered in 1972, but this is likely referring to the original TTL implementation. It goes on to note that an effort to reduce the processor to a two-chip implementation with deliveries in COS/MOS in 1974. It is here that the processor is first referred to as COSMAC, for COmplementary-Symmetry-Monolithic-Array Computer. It goes on to state that another lab will be producing the system in an 8-chip silicon-on-sapphire format, although the date is simply "soon after" the CMOS versions, and that plans for a single-chip version were already being planned.
COSMAC devices
Although RCA began the development of the COSMAC in the early 1970s, it was some time before they introduced their own products based on it. In 1975, a prototype of an arcade game machine with swappable ROMs was experimented with for the coin-op business, but was ultimately abandoned.Meanwhile, Weisbecker had adapted the original FRED, known within RCA as System 00 by this time, using the new chipset to produce a greatly simplified single-board system known as then COSMAC ELF. Building instructions were described in an article in Popular Electronics magazine in 1976, and an expanded version with various upgrades in a second article in 1977. A unique feature of the ELF is that it did not require any read only memory for startup, instead, the processor's direct memory access system was used to read front-panel switches directly into memory.
RCA debated whether to introduce pre-packaged versions of the ELF to the market. While they debated, further development led to a simplified machine combining the ELF with a new display driver chip, the CDP1861, to produce a game console. During this time, Joyce Weisbecker was hired by RCA to write several videogames for the platform, including a quiz-style educational product in partnership with Random House, one of the many companies that had been picked up by RCA's buying sprees.
After a year of discussion, the company eventually decided to release two mass-market products based on the platform, a kit computer known as the COSMAC VIP, and a game console known as the RCA Studio II. The machines had been available since 1975, but the Studio II was announced only in January 1977, a couple of months after the Fairchild Channel F became the first cartridge-based machine on the market. Both would soon be eclipsed and largely forgotten due to the release of the Atari 2600 later that year. RCA canceled the Studio II in February 1978.
RCA also released a series of modular computer systems, based on the RCA Microboard form factor from the 1802's initial release, up until the collapse of RCA itself. These were mainly aimed at industrial applications and systems development, and were highly configurable.
Embedded use
The COSMAC would find great success in the embedded market, because its CMOS design allowed it to work at lower power. By the late 1970s it was widely used in many industrial settings, and especially aerospace. Multiple 1802s were used as auxiliary IO processors in the Galileo probe to Jupiter in 1989, and it remains in use in similar roles as of 2017.Applications
Microcomputer systems
A number of early microcomputers were based on the 1802, including the COSMAC ELF, Netronics ELF II, Quest SuperELF, COSMAC VIP, Comx-35, Finnish Telmac 1800, Telmac TMC-600 and Oscom Nano, Yugoslav Pecom 32 and 64, and the CyberVision 2001 systems sold through Montgomery Ward in the late 1970s, as well as the RCA Studio II video game console. The Edukit single-board computer trainer system, similar to an expanded COSMAC ELF, was offered by Modus Systems Ltd. in Britain in the early 1980s. Infinite Incorporated produced an 1802-based, S-100 bus expandable console computer trainer in the late 1970s called the UC1800, available assembled or in kit form.As part of 1802 retrocomputing hobbyist work, other computers have been built more recently, including the Membership Card microcomputer kit that fits in an Altoids tin and the Spare Time Gizmos Elf 2000, among others. See for other systems.
Product integration
The 1802 was used in scientific instruments and commercial products.The 1802 was used in Plessey payphones.
Post-1980 Chrysler and associated model vehicles use the 1802 in their second-generation Electronic Lean-Burn System, with electronic spark control, one of the first on-board auto computer-based control systems.
The 1802 was used in the manufacture of pinball machines and video arcade games in Spain.
Radiation hardening
A high-speed version of the 1802 was fabricated in Silicon on Sapphire semiconductor process technology, which gives it a degree of resistance to radiation and electrostatic discharge. A different radiation-hardened version of the 1802, developed jointly by RCA and Sandia National Laboratories, was built on bulk silicon using C2L technology. Along with its extreme low-power abilities, this makes the chip well-suited in space and military applications..Space technology and science
The 1802 was used in many spacecraft and space science programs, experiments, projects and modules such as the Galileo spacecraft, Magellan, the Plasma Wave Analyzer instrument on ESA's Ulysses spacecraft, various Earth-orbiting satellites and satellites carrying amateur radio.Several subsystems of NASA's Hubble Space Telescope use 1802 processors, including the WFPC
and the MATs.
Military uses
A number of British military items from the 1980s and 1990s used the 1802, amongst them:- L1A1 Fuze Setter
- SAWES training system fitted to SLR / SA80 rifles
- Ptarmigan battlefield communications system
Programming languages
Interpreter for Process Structures, a programming language and development environment, was specifically written and used for real-time control of AMSAT satellites.