The Ferranti F100-L was a 16-bit microprocessor family announced by Ferranti in 1976 which entered production in 1977. It was the first microprocessor designed in Europe, and among the first 16-bit single-chip CPUs. It was designed with military use in mind, able to work in a very wide temperature range and radiation hardened. To deliver these capabilities, the F100 was implemented using bipolar junction transistors, as opposed to the metal oxide semiconductor (MOS) process used by most other processors of the era. The family included a variety of support chips including a multiply/divide unit, various memory support chips, timers and serial bus controllers.
The F100 was priced at £39 in 1978 in 100-off quantities. Three models were offered at the same price; the commercial spec was rated at 8 MHz, industrial at 6.5 MHz at an extended temperature range, and military spec at 3.5 or 5 MHz with a temperature range from -55 C to +125 C. It was very cost competitive in the industrial and military markets, but less so in the commercial market where processors like the MOS 6502 were about $11 in the same 100 unit quantity.
The line was updated with the F200-L in 1984. This was software compatible with the F100, but included the maths processor on the same die, expanded addressing to 128 kB, and allowed up to 1 MB of memory when paired with the new F220 memory management unit. Shortly after the F200 came to market, in 1987 Ferranti purchased International Signal and Control, a company soon discovered to be committing large amounts of fraud; this drove Ferranti into bankruptcy.
The chip division was purchased by Plessey who continued producing some of the F100 family support chips as late as 1995. Owing to it being used almost entirely in the military realm, the F100 is little known in the wider retrocomputing field and few examples remain.
History
Previous computers
Ferranti was among the first companies to introduce a commercial computer, the Ferranti Mark 1 of 1951. They followed this with several other commercial designs, most notably the Ferranti Atlas of 1962, for a time the fastest computer in the world. In 1963 they used the Ferranti-Packard 6000, developed independently at their Canadian division, as the "golden brick" in the sale of their entire commercial computing line to International Computers and Tabulators (ICT). ICT used the FP6000 as the basis for their 1900 line, which sold for years. Prior to the sale, Ferranti sold about 24% of all computing hardware in the UK.
As part of the deal with ICT, Ferranti were barred from sales into the commercial computer market. This left them with two existing architectures that had been developed for military uses, the small Ferranti Argus that had already become a success in the industrial controller market, and the FM 1600, a larger machine used for realtime data handling, weapons control and simulation. Both were built of individual transistors and small scale integration integrated circuits using Ferranti's MicroNor bipolar transistor process. These were both very successful in the market, generating hundreds of millions of pounds of sales through the late 1960s.
CDI
A significant problem with the MicroNor process was that a logic gate implemented using bipolar layout was significantly larger than one using the contemporary MOSFET process, about six times. In typical designs, the bipolar layout also required three or four extra masking steps, each of which was time-consuming and increased the possibility of the chip being damaged during processing. Experience with MicroNor suggested that a maximum of about 100 gates was the limit for a single chip, in contrast to MOS, which was being used for designs with thousands of gates. However, the MOS system was more sensitive to impurities in the semiconductor feedstock, which led to electrical noise that reduced performance and also limited its operating conditions. Neither was acceptable in the military market.
In 1971, Ferranti licensed the new collector-diffusion-isolation (CDI) process from Fairchild Semiconductor. This process, originally developed at Bell Labs, produced a dramatically simplified bipolar gate which required fewer masking steps and was only slightly larger than the equivalent MOS. This was of little interest to either Bell or Fairchild, who were happy with their MOS processes, and neither had progressed beyond experimental systems.