The Ferranti F100-L was a
16-bit
16-bit microcomputers are microcomputers that use 16-bit microprocessors.
A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two mos ...
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
family announced by
Ferranti
Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index.
The firm was known ...
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
Radiation hardening is the process of making electronic components and circuits resistant to damage or malfunction caused by high levels of ionizing radiation ( particle radiation and high-energy electromagnetic radiation), especially for enviro ...
. To deliver these capabilities, the F100 was implemented using
bipolar junction transistor
A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar ...
s, as opposed to the
metal oxide semiconductor
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the thermal oxidation, controlled oxidation of silicon. It has an insulated gate, the ...
(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
In telecommunication and data transmission, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are ...
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
The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small te ...
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
A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical ad ...
. Shortly after the F200 came to market, in 1987 Ferranti purchased
International Signal and Control
International Signal and Control (ISC) was a United States, U.S. defense contractor based in Lancaster, Pennsylvania that was involved in the manufacture of electronic missile subassemblies, navigation components, fuses, power supplies for proximit ...
, a company soon discovered to be committing large amounts of fraud; this drove Ferranti into bankruptcy.
The chip division was purchased by
Plessey
The Plessey Company plc was a British electronics, defence and telecommunications company. It originated in 1917, growing and diversifying into electronics. It expanded after World War II by acquisition of companies and formed overseas compani ...
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
Retrocomputing is the use of older computer hardware and software in modern times. Retrocomputing is usually classed as a hobby and recreation rather than a practical application of technology; enthusiasts often collect rare and valuable hardw ...
field and few examples remain.
History
Previous computers
Ferranti
Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index.
The firm was known ...
was among the first companies to introduce a commercial computer, the
Ferranti Mark 1
The Ferranti Mark 1, also known as the Manchester Electronic Computer in its sales literature, and thus sometimes called the Manchester Ferranti, was produced by British electrical engineering firm Ferranti Ltd. It was the world's first commer ...
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
The FP-6000Ferranti Packard: Pioneers in Canadian Electrical Manufacturing Norman R Ball, John N Vardalas
was a second-generation Mainframe computer, mainframe computer developed and built by Ferranti-Packard, the Canadian division of Ferranti, ...
, developed independently at their Canadian division, as the "golden brick" in the sale of their entire commercial computing line to
International Computers and Tabulators
International Computers and Tabulators or ICT was a British computer manufacturer, formed in 1959 by a merger of the British Tabulating Machine Company (BTM) and Powers-Samas. In 1963 it acquired the business computer divisions of Ferranti. It ...
(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
Ferranti's Argus computers were a line of industrial control computers offered from the 1960s into the 1980s. Originally designed for a military role, a re-packaged Argus was the first digital computer to be used to directly control an entire fact ...
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
transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...
s and
small scale integration integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
s using Ferranti's MicroNor
bipolar transistor
A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar t ...
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
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
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
Fairchild Semiconductor International, Inc. was an American semiconductor company based in San Jose, California. Founded in 1957 as a division of Fairchild Camera and Instrument, it became a pioneer in the manufacturing of transistors and of int ...
. This process, originally developed at
Bell Labs
Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984),
then AT&T Bell Laboratories (1984–1996)
and Bell Labs Innovations (1996–2007),
is an American industrial research and scientific development company owned by mult ...
, 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.
Ferranti invested heavily in the CDI process, working to raise the operating voltage from 3 to 5V for compatibility with their existing
transistor-transistor logic (TTL) devices that were already widely used in military applications. This led to a series of
medium scale integration
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny M ...
parts using the process. Most well known among these was a series of
uncommitted logic arrays (ULA, or gate array), chips with no pre-set logic design that could be programmed by the developer to produce any required circuit. These became very popular, and by 1986 the company held about 20% of the worldwide market for ULAs.
F100-L
The introduction of the first
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
s in the early 1970s cut into Ferranti's military computing business. While these early designs were not competitive in performance terms, their
price/performance ratio was orders of magnitude better than Ferranti's discrete designs, in spite of several rounds of cost-reduction in the MicroNor line in the late 1960s. Convinced that the microprocessor represented a strategic change in military applications, in 1974 the
UK Ministry of Defence
The Ministry of Defence (MOD or MoD) is the department responsible for implementing the defence policy set by His Majesty's Government, and is the headquarters of the British Armed Forces.
The MOD states that its principal objectives are to ...
agreed to sponsor an effort by Ferranti to produce a military-grade microprocessor design using the CDI process, whose high power-handling allowed them to operate in electrically noisy environments.
An internal survey within the company suggested that an 8-bit part would not have the capability needed by the various divisions, and the decision was made to produce a 16-bit part. Based on studies of the economics of chip fabrication, Ferranti concluded that they had a budget of about 1,000 gates before the design would be too expensive. To produce a 16-bit design with this limited gate count, the
arithmetic logic unit
In computing, an arithmetic logic unit (ALU) is a Combinational logic, combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers. This is in contrast to a floating-point unit (FPU), which operates on ...
, or ALU, had to operate in a bit-serial fashion. This slows the performance of mathematical operations, so that the minimum time needed to complete an instruction is 36 clock cycles. This performance hit is offset somewhat by the 8 MHz clock speed, roughly double that of the fastest CPUs of the era.
With 16-bit data and 15-bit addresses, normally 31 pins would be required to interface the design to the computer as a whole. Desiring a low-cost solution, it had to fit into a conventional 40-pin
dual in-line package
In microelectronics, a dual in-line package (DIP or DIL), is an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board (P ...
(DIP). To accomplish this, the data and address lines share pins, and thus require multiple cycles to complete the reading of a single instruction. For comparison, the
Texas Instruments TMS9900
Introduced in June 1976, the TMS9900 was one of the first commercially available, single-chip 16-bit microprocessors. It implemented Texas Instruments' TI-990 minicomputer architecture in a single-chip format, and was initially used for low-end ...
, another 16-bit design introduced the same year, had double the gate count and was packaged in an expensive custom 64-pin DIP.
Ultimately the F100 failed to meet its 1,000 gate limitation and was built with about 1,500 gates on a 5.8 mm square surface. This was larger than their existing mask-production system and required them to develop a new version with a larger optical reduction ratio. The timing of the design effort also produced one advantage; the F100 was beginning to be readied for production just as the
Micralign
The Perkin-Elmer Micralign was a family of aligners introduced in 1973. Micralign was the first projection aligner, a concept that dramatically improved semiconductor fabrication. According to the Chip History Center, it "literally made the modern ...
system was coming to market, and Ferranti adopted this projection alignment system for production, thereby greatly improving yields.
As was common at the time, the F100 was introduced along with a family of support chips, including memory bus interfaces, interrupt controller, a
direct memory access
Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU).
Without DMA, when the CPU is using programmed input/output, it is t ...
controller and a basic
serial bus
In telecommunication and data transmission, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are ...
controller. Most of these were built using their ULA chips. Perhaps most interesting among these was the F101-L, released shortly after the CPU, which performed hardware multiplication and division. This became so common that the CPU was soon offered with the F101 on the same die, as the FBH5092.
While the F100 was being developed, Ferranti produced a multi-card rackmount version of the CPU, the F100-M. This was used as a development platform and saw some civilian use as well. Programming tools were initially written in
FORTRAN, but most projects were written in
CORAL
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
once a compiler for that language became available.
When it was first announced in 1977, 100-unit lots were priced at £57, but that was soon reduced to £39 by 1978. A set containing an F100 along with the F111-L control interface and two F112-L DMA controllers was available for an additional £18. While this made it uncompetitive with MOS-based commercial processors like the $25
Zilog Z80
The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples wer ...
or $11
MOS 6502
The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small te ...
in the same 100-unit lots, it was very competitive with other military-spec designs like the Z80's military-rated unit at $165.
The F100 quickly found use in UK defense projects. Among the more well-known successes was the guidance unit for the
Sea Eagle
A sea eagle or fish eagle (also called erne or ern, mostly in reference to the white-tailed eagle) is any of the birds of prey in the genus ''Haliaeetus'' in the bird of prey family Accipitridae.
Taxonomy and evolution
The genus ''Haliaeetus'' ...
missile. Other examples include the gunnery computer for the
Falcon
Falcons () are birds of prey in the genus ''Falco'', which includes about 40 species. Falcons are widely distributed on all continents of the world except Antarctica, though closely related raptors did occur there in the Eocene.
Adult falcons ...
self-propelled anti-aircraft gun, a variety of ballistics computers used in various tanks, the CPU for the
UoSAT-1
UoSAT-1, also known as UoSAT-OSCAR 9 (UO-9), was a British amateur radio satellite which orbited Earth. It was built at the University of Surrey and launched into low Earth orbit on 6 October 1981. It exceeded its anticipated two-year orbital li ...
satellite, and a number of naval computer applications. It was also used in the civilian field in engine management systems from Ultra Electronic Controls, a propeller speed limiter from Dowty Group, and even control of nuclear test equipment using the
CAMAC protocol.
F200-L
The F100 line was updated in 1984 with the introduction of the F200-L, which was software and pin-compatible with the F100. The primary changes were to include the math processor, formerly the F101, as part of the base CPU. Improvements in fabrication also allowed the F200-L to run up to 20 MHz. The F200 also supported the 16th bit in addresses, expanding the memory to 64 kW (128 kB). The new F220-L memory management unit, launched at the same time, provided address lookup within a 1 MW (2 MB) memory space.
Plessey purchase
During the 1980s, Ferranti was very successful and cash-flush. Desiring to make more sales into the United States, the company began looking for an established US military supplier they could buy and use as the basis for their own division in the country. This process eventually led them to purchase
International Signal and Control
International Signal and Control (ISC) was a United States, U.S. defense contractor based in Lancaster, Pennsylvania that was involved in the manufacture of electronic missile subassemblies, navigation components, fuses, power supplies for proximit ...
(ISC) in 1987, and along with it, changing the name of the company to Ferranti International.
[
Unfortunately, ISC's major business, unrevealed at the time, was illegal arms sales. This source of income evaporated with the purchase, leaving them with practically no ongoing business. A lengthy court process ensued, and the debt load of the purchase along with the cost of the litigation drove Ferranti into bankruptcy in December 1993.]
As part of the bankruptcy proceedings, the company was broken up, and the semiconductor division was purchased by Plessey
The Plessey Company plc was a British electronics, defence and telecommunications company. It originated in 1917, growing and diversifying into electronics. It expanded after World War II by acquisition of companies and formed overseas compani ...
. This was subsequently part of the Siemens Plessey
Siemens Plessey was the name given to the Plessey assets acquired by Siemens in 1989. Today most of these units are part of BAE Systems while some units are now part of EADS.
History
Background : before 1989
The history of the evolution of Sieme ...
unit after Siemens purchased the company in 1989. The line continued to be produced through this period, with the F100/200 itself being produced until at least 1992, and some of the other members until 1995.
Today
Used primarily in military systems, few F100 systems remain today. Among the few are a display F100-L chip at the Museum of Science and Industry in Manchester, and a small number of cards from a F100 microcomputer at the Centre for Computing History
The Centre for Computing History is a museum in Cambridge, England, established to create a permanent public exhibition telling the story of the Information Age.
Overview
The museum acts as a repository for vintage computers and related artefa ...
.
Description
Registers
Most microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
s of the 1970s used internal 8-bit wide processor register
A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-only. ...
s, an 8-bit data bus
In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This e ...
and a 16-bit address bus
In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ex ...
. The F100 used 16-bit registers but only 15-bits in the address bus, but these addresses represented 16-bit words so the total addressable memory was 64 kB, as was the case with most 8-bit processors with 16-bit addressing. At the time the F100 was designed, memory was extremely expensive and typical machines of the era generally featured only 4 kB of SRAM, so the missing 16th bit in the address was not an important consideration.
There are three main user registers. The 16-bit ACC ( accumulator) and OR (operand register) are used to hold values being manipulated by the arithmetic logic unit
In computing, an arithmetic logic unit (ALU) is a Combinational logic, combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers. This is in contrast to a floating-point unit (FPU), which operates on ...
(ALU) during calculations and comparisons. The results of these operations set bits in the 7-bit CR (condition register). Two additional registers are used internally; the 15-bit PC (program counter
The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 and Itanium microprocessors, and sometimes called the instruction address register (IAR), the instruction counter, or just part of the instruction sequencer, is ...
) holds the address of the currently executing instruction and has an auto-increment feature, while the 16-bit IR (instruction register) is used to hold the actual instruction itself. If the instruction operates on a memory address, the value in the IR is moved to internal latches and the IR is then loaded with the address value.
The CR contained a set of seven bits:
Addressing modes
The F100 had a total of four addressing mode
Addressing modes are an aspect of the instruction set architecture in most central processing unit (CPU) designs. The various addressing modes that are defined in a given instruction set architecture define how the machine language instructions in ...
s; direct, immediate, pointer and immediate indirect.
Direct mode encoded a constant value directly into the instruction. To do this, only the upper five bits were available for the opcode, allowing a total of 32 possible direct instructions, while the remaining lower 11 bits stored the numeric value. In the standard assembler mnemonics, this was indicated by placing the value directly after the instruction. For instance, AND 0x444
would perform a bitwise AND
In computer programming, a bitwise operation operates on a bit string, a bit array or a binary numeral (considered as a bit string) at the level of its individual bits. It is a fast and simple action, basic to the higher-level arithmetic oper ...
operation between the current value in the ACC and the 16-bit constant 0x444. Immediate mode was similar to direct, but the value to be accessed is placed in the 16-bits following the instruction in order to allow larger constants. This was indicated with a comma, for instance, AND ,0x4444
.
As was common at the time, the F100 featured a form of zero page
The zero page or base page is the block of memory at the very beginning of a computer's address space; that is, the page whose starting address is zero. The size of a page depends on the context, and the significance of zero page memory versus h ...
addressing they referred to as Pointer Indirect Addressing, or simply pointer. Address zero, a 16-bit word, was used as the stack pointer
In computer science, a call stack is a stack data structure that stores information about the active subroutines of a computer program. This kind of stack is also known as an execution stack, program stack, control stack, run-time stack, or mach ...
, which lacked its own register. This had to be set to an odd number. Locations 1 through 255 were available for the user. Pointer addressing used the lower 8 bits of the instruction to indicate one of the zero page addresses, whose value would be read as an address, and then the value at that address would be loaded. Pointer addressing was indicated with a slash, for instance, AND /0x44
.
Additionally, the F100 had alternate forms of the pointer addressing instructions that performed a pre-increment or post-decrement of the value in the pointer in the zero page. These make it easy to perform loops over blocks of data in main memory without needing a separate increment operation to be read and performed. These were indicated using the + or - at the end of the pointer value, for instance, AND /0x44+
or AND /0x44-
.
Finally, indirect addressing was similar to pointer addressing but allows any value in memory to hold the pointer, rather than just the zero page. This is more flexible, but as the address is stored in the 16 bits following the instruction, using this method is slower than zero page because two memory addresses have to be read instead of one. This mode was specified with a dot, for instance, AND .0x4444
.
Some of the indirect addressing mode instructions also took a third value, indicating another location in memory. This was used for bitwise comparisons; the instructions included which bit to be tested as the first operand, the location in memory as the second, and the address to jump to as the third. For instance, JBS 0x2 0x4444 0x5555
would test the second bit of the value in location 0x4444 and then jump to location 0x5555 if it was set, or continue on if it was not.
Because the addressing format in the instructions varied in length, memory was naturally broken into segments. The first was the stack pointer in location zero, next was the remaining 255 locations of the zero page, then the maximum 2048 locations of the direct mode (which included the zero page), and finally the remaining memory which could be accessed by the 15-bit addresses.
Instructions
The F100 had a total of 29 instructions, which combined using the various addressing modes results in 153 opcodes. The instructions generally fall into six main categories; math and logical, double-length (32-bit) math and logical, bit tests and conditional branches, interrupt handling, and external functions. The later allows unused bits of the instruction to be passed to external chips for processing.
The instructions were relatively common but had some variations. For instance, and had alternate versions, and , which performed the operation and then stored the result back into the operand address. performed an unconditional jump, while called a subroutine, what most assemblers would call a , and performed a return. Conditional branches allowed test-and-jump.
The instruction format used various fields to encode instructions classes. The four most significant bits, 15 through 12, selected the actual instruction, for instance, 1001 was . The rest of the bits varied depending on the addressing mode. For instance, if direct addressing was being used, bit 11 was set to 0, 10 and 9 to 1, and the remaining 11 bits encoded the address of the operand. If the 11 bits were all set to zero, it instead read the operand from the next 16 bits in memory.
Start up
On startup or reset, the processor examines the AdSel pin (address select). If the pin voltage represents a zero, it jumps to location , or 16384 decimal, while if the pin is 1, it jumps to , 2048. By placing startup code in ROM at those locations, the boot process can be automated.
Notes
References
Citations
Bibliography
*
*
* {{cite web
, first=Richard , last=Evans
, title=The Ferranti F100-L Microprocessor
, url=https://revaldinho.github.io/f100l/doc/F100CPU.html
, date=2016
External links
The Ferranti F100-L Microprocessor
source code for a F100-L emulator written in Python.
The Ferranti F100-L CPU at The ICL Computer Museum
16-bit microprocessors
Ferranti computers