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Fairchild F8
The Fairchild F8 is an 8-bit microprocessor system from Fairchild Semiconductor, announced in 1974 and shipped in 1975. The original processor family includes four main 40-pin integrated circuits (ICs); the 3850 CPU which contains the arithmetic logic unit and a scratchpad, the 3851 Program Storage Unit (PSU) which contains 1 KB of program ROM and handles instruction decoding, and the optional 3852 Dynamic Memory Interface (DMI) or 3853 Static Memory Interface (SMI) to control additional RAM or ROM holding the user programs or data. The 3854 DMA is another optional system that adds direct memory access into the RAM controlled by the 3852.
A minimal system containing a 3850 and 3851 also included four 8-bit data ports, 64 bytes of RAM, and a user program on ROM. This allowed microcontroller applications to be built using just two chips. Doing the same on more traditional designs like the 8080 or 6800 normally required seven. It also meant that any application that did not fit the simple requirements generally required at least three 40-pin ICs, the CPU, PSU and either the 3852 or 3853 along with additional memory chips. As a result of these tradeoffs, the F8 series found widespread use in the microcontroller market but saw less use as a CPU in general-purpose computers. It is relatively obscure today, as its embedded uses rarely revealed the F8 inside.
In 1977, Mostek released a significantly improved implementation, the Mostek 3870. It merged the 3850 and 3851 into a single chip and reduced the number of power supply voltages needed. More important, Mostek re-arranged the assembly line so user code in ROM was added at the last step, greatly reducing the cost of customizing the design for controller use. The 3870 replaced the original Fairchild versions and was produced by several companies in the US and Europe. In Europe, STMicroelectronics continued producing variations of the design into the mid-1990s.
The F8 story begins with a microprocessor development project at Olympia-Werke, a subsidiary of AEG. Best known as a manufacturer of typewriters, Olympia also had a long history in mechanical calculators, a market that was rapidly converting to electronic versions. Olympia was developing a processor system known as the CP3-F, which General Instrument (GI) had licensed from them. As part of the license agreement, GI sent David Chung, head of GI's processor division, to Olympia to liaise with their design team. Shortly after returning to the US, Chung quit GI and moved to Fairchild where he became lead designer of the F8, and is named as the primary inventor on the patent.
Fairchild announced the F8 in September 1974, which led almost immediately to a lawsuit from GI for the misappropriation of trade secrets. As the case dragged on, in February 1976 Fairchild announced a cross-licensing deal with Olympia for the F8, meaning they now had legal access to the original CP3F design and GI's lawsuit was neutered, at least in technical details. Very little information on the CP3F is available, but it is widely believed by industry observers that the CP3F is the basis for the F8 design. The court case dragged on into the 1980s, but with no technical issues of note, it had no effect on the sales of the F8.
GI put the original design on the market as the General Instrument 8000. This had some success in Europe, but was no longer actively marketed by 1977 as the F8 took its sales.
The first engineering samples of the F8 were sent out in April 1975, with volume shipments beginning that fall. At the time, the electronics industry demanded second source arrangements as insurance that the design would not disappear if the designing company went bankrupt or simply lost interest in the design. Fairchild announced such an agreement with Mostek in June 1975. The agreement allowed both companies to continue independent development of the design. The F8 would eventually be produced by Motorola and SGS as well.
The F8 was introduced at a single-unit price of US$130 (equivalent to $777.83 in 2025), making it less expensive than contemporary designs like the Intel 8080 or Motorola 6800 which were at least twice that price. Additionally, the minimal system included four 8-bit input/output ports, a small amount of RAM, and 1 KB of ROM. Together, they allowed simple applications to be built with only two ICs. In contrast, designs like the 8080 and 6800 required separate dedicated-purpose ICs to provide these functions, normally seven, so an F8 system could be implemented for far less total cost. Offsetting this to some degree was that the program ROM in the PSU was masked onto the chips early in the production process, which required separate production lines for each customer. As a result, setup fees were on the order of $10,000 to 15,000. Prices for the 3850 continued to fall through its production run. By 1977, it was selling for $9.95 in 100-unit quantities.
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Fairchild F8 AI simulator
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Fairchild F8
The Fairchild F8 is an 8-bit microprocessor system from Fairchild Semiconductor, announced in 1974 and shipped in 1975. The original processor family includes four main 40-pin integrated circuits (ICs); the 3850 CPU which contains the arithmetic logic unit and a scratchpad, the 3851 Program Storage Unit (PSU) which contains 1 KB of program ROM and handles instruction decoding, and the optional 3852 Dynamic Memory Interface (DMI) or 3853 Static Memory Interface (SMI) to control additional RAM or ROM holding the user programs or data. The 3854 DMA is another optional system that adds direct memory access into the RAM controlled by the 3852.
A minimal system containing a 3850 and 3851 also included four 8-bit data ports, 64 bytes of RAM, and a user program on ROM. This allowed microcontroller applications to be built using just two chips. Doing the same on more traditional designs like the 8080 or 6800 normally required seven. It also meant that any application that did not fit the simple requirements generally required at least three 40-pin ICs, the CPU, PSU and either the 3852 or 3853 along with additional memory chips. As a result of these tradeoffs, the F8 series found widespread use in the microcontroller market but saw less use as a CPU in general-purpose computers. It is relatively obscure today, as its embedded uses rarely revealed the F8 inside.
In 1977, Mostek released a significantly improved implementation, the Mostek 3870. It merged the 3850 and 3851 into a single chip and reduced the number of power supply voltages needed. More important, Mostek re-arranged the assembly line so user code in ROM was added at the last step, greatly reducing the cost of customizing the design for controller use. The 3870 replaced the original Fairchild versions and was produced by several companies in the US and Europe. In Europe, STMicroelectronics continued producing variations of the design into the mid-1990s.
The F8 story begins with a microprocessor development project at Olympia-Werke, a subsidiary of AEG. Best known as a manufacturer of typewriters, Olympia also had a long history in mechanical calculators, a market that was rapidly converting to electronic versions. Olympia was developing a processor system known as the CP3-F, which General Instrument (GI) had licensed from them. As part of the license agreement, GI sent David Chung, head of GI's processor division, to Olympia to liaise with their design team. Shortly after returning to the US, Chung quit GI and moved to Fairchild where he became lead designer of the F8, and is named as the primary inventor on the patent.
Fairchild announced the F8 in September 1974, which led almost immediately to a lawsuit from GI for the misappropriation of trade secrets. As the case dragged on, in February 1976 Fairchild announced a cross-licensing deal with Olympia for the F8, meaning they now had legal access to the original CP3F design and GI's lawsuit was neutered, at least in technical details. Very little information on the CP3F is available, but it is widely believed by industry observers that the CP3F is the basis for the F8 design. The court case dragged on into the 1980s, but with no technical issues of note, it had no effect on the sales of the F8.
GI put the original design on the market as the General Instrument 8000. This had some success in Europe, but was no longer actively marketed by 1977 as the F8 took its sales.
The first engineering samples of the F8 were sent out in April 1975, with volume shipments beginning that fall. At the time, the electronics industry demanded second source arrangements as insurance that the design would not disappear if the designing company went bankrupt or simply lost interest in the design. Fairchild announced such an agreement with Mostek in June 1975. The agreement allowed both companies to continue independent development of the design. The F8 would eventually be produced by Motorola and SGS as well.
The F8 was introduced at a single-unit price of US$130 (equivalent to $777.83 in 2025), making it less expensive than contemporary designs like the Intel 8080 or Motorola 6800 which were at least twice that price. Additionally, the minimal system included four 8-bit input/output ports, a small amount of RAM, and 1 KB of ROM. Together, they allowed simple applications to be built with only two ICs. In contrast, designs like the 8080 and 6800 required separate dedicated-purpose ICs to provide these functions, normally seven, so an F8 system could be implemented for far less total cost. Offsetting this to some degree was that the program ROM in the PSU was masked onto the chips early in the production process, which required separate production lines for each customer. As a result, setup fees were on the order of $10,000 to 15,000. Prices for the 3850 continued to fall through its production run. By 1977, it was selling for $9.95 in 100-unit quantities.