30 years ago this
month, two men met at an IFIP meeting in Canada. The consequences of that meeting made an
impact on the face of the electronics industry. Dick Selwood looks at Inmos and its legacy
The way Iann Barron tells it, his first meeting with Dick Petritz should have been an
omen. Iann had been tasked with organising a session on the future of computers at
IFIPs conference in Toronto in 1977 and he asked Dr Petritz, who had been at Texas
Instruments and was now a venture capitalist, to present a paper on semiconductors. The
programme was printed, with Dr Petritz name in it, but Iann never heard from him
until he arrived at the conference and gave his paper. During the after-session drinks
with the speakers, Petritz asked Iann if he wanted to start a semiconductor company, with
his role being to develop a microprocessor.
The company was eventually funded by the British Government through the (now extinct)
National Enterprise Board in 1978. A site in the US covered memory design, process
development and initial manufacturing, while a UK design centre in Bristol worked on the
microprocessor and the UK manufacturing facility was in a Richard Rogers designed factory
in Newport, South Wales.
There were always tensions. The Thatcher Government, elected in May 1979, was very unhappy
at inheriting the company. Their representatives on the companys board, the
NEB-appointed external directors, knew nothing about the semiconductor industry. And there
was a cultural split between the US engineers and the UK scientists, which personality
clashes between Iann Barron and the third founder, memory guru Paul Schroeder, did nothing
The US management never understood that the UK Government wasnt a normal venture
capitalist but was expecting much more than a return on capital, looking for technology
transfer to help move Britain forward in electronics technology and for thousands of jobs.
The UK press were expecting Inmos to produce a 64kbit dynamic RAM, then regarded as
leading edge, and couldnt understand that a 16k SRAM was at least as complex and
potentially more profitable.
And the transputer was a mystery to everyone.
Iann Barrons vision was of an element that would both carry out what we would today
consider a form of digital signal processing and would also, through simple interfaces,
link with other transputers to produce a parallel processing array whose throughput scaled
almost linearly with the number of elements. Many parallel processing architectures have
extensive communication overheads, so adding a new element doesnt always create a
significant increase in power, and in some early experiments could even reduce processing
available for the application.
To design the transputer, the Bristol team first created a design system. (The US memory
design teams still used draughtsmen, as their effort was in tuning the memory cell and
then creating an array.) With the system, a team under David May created the architecture
of the transputer and Inmos also developed a programming language, occam. Both had
inherent parallelism based on the theory of Communicating Sequential Processes (CSP)
developed by Tony Hoare (now Professor Sir C. A. R. Hoare, Senior Researcher with
Microsoft in Cambridge). To add to the complexity of the task, the team also had to design
a development environment including a work station. The same team was also responsible for
a graphics processing engine family.
While this was moving forward at Bristol, the US designed and launched the 16k SRAM. After
a slow start it became a commercial success, with over a quarter of the market and some
very good margins, helped by Intel, then the memory market technology leader, failing to
ship their own device. The 64k DRAM was moderately successful in a much more crowded
field, as by this time the Japanese were gearing up their fabs with DRAM and getting far
better yields than many US fabs.
On the political level, the American management tried to organise a buy-out of the
American operation and failed. The NEB, after nearly paying a US electronics company to
take Inmos off their hands was preparing the company for a US stock market flotation or
for the sale of a significant stake to an industrial consortium. Then Thorn EMI, in 1984,
made an offer that not only solved the Governments problem of what to do with Inmos,
but gave them a £30 million profit on their £65 million investment and took £35 million
of loan guarantees (secured on highly in-demand chip-making equipment) from the public
Thorn EMI and its first appointee as Inmos chairman also knew little about semiconductors,
and didnt realise that much of the product development, including test chips for the
transputer, had been held up when manufacturing capacity was used to ship as much product
as possible into a boom market, making the company as attractive as possible for a
floatation. When the inevitable market downturn followed, Inmos was left with few new
products and it wasnt until a year later that the first transputer chips, in the
T400 family, were ready to be shipped.
Transputers were successful for a number of applications: the IBM PC used the graphics
engine and many laser printers were powered by transputers. But Thorn EMIs own
problems meant that was insufficient capital to develop the transputer family properly.
The T800 moved the product forward with a 64-bit floating point unit, but it wasnt
until after Thorn EMI transferred Inmos into STs (then SGSThompson) ownership, that
the next generation, the T9000, appeared in 1992. By then it was not sufficiently powerful
to provide an incentive for developers to take on what they perceived as the difficult
task of learning how to programme parallel systems.
ST pulled the plug on further transputer development and Inmos staff were deployed in a
variety of other activities, including more graphics controller chips. Both the
manufacturing plants were sold, with Colorado Springs going first to Cray Computer and
then to a succession of other companies. The Newport facility was first run as a pure play
foundry with several owners and is now owned by International Rectifier.
Today Inmos doesnt exist as an entity, but there is a significant legacy.
The Inmos legacy has several threads. There are companies that were founded by Inmos
people, there are the companies where Inmos staff have entered senior positions and there
is the more intangible area of the influence that Inmos has had on the electronics
industry as a whole. Also there is space, where Inmos products are still in service and
Inmos ideas are exercising an influence on the development of space technology.
The first Inmos spin-off was transputer based, but was a memory company. Rahul Sud, who
had been active in the 16k SRAM design and then in a failed design for a 64k EEPROM
founded Lattice to work on EEPROM, attracting a number of Inmos process technologists to
the new company.
The first transputer company was Meiko. In the internal politics that followed
Thorns attempts to understand and manage Inmos, a small group from the transputer
team left to create supercomputers with multiple transputers. It supplied systems to major
power users. In an attempt to break into the American market, it registered as an American
company, and then found itself ruled out of a project for the Meteorological Office. Meiko
is now part of Quadrics, itself part of Finmeccanica, still working on powerful processing
Another company created by people from the Bristol design centre was Division, exploiting
virtual reality, which went public and was taken over by Parametric Technology. People
from Division founded PixelFusion, now ClearSpeed, which uses massively parallel
processing to create coprocessors and acceleration boards.
Motion Media (now part of Scotty Group) was another Inmos child, developing video
communication networking. Their videophone technology is now available from AuPix. A
spin-off from Motion Media was EsGem, who were developing a technology for tracking issues
in networked products.
The Inmos family tree continues with XMOS, which has just been launched with David May,
now Professor and Head of Computer Science at Bristol University, as CTO (see box).
All those companies are in the Bristol area, and like the other two areas where Inmos had
operations, Newport in South Wales and Colorado Springs, it is now a technology hotspot.
As well as the direct spin-offs, other companies have located operations in the area to
fish in the pool of skilled labour, using the same dynamics as made Silicon Valley such a
The Bristol area has ST, obviously. Other multinationals include HP, Infineon, and
Toshiba. Element 14, once part of Acorn/ARM, set up a design centre using ex-Inmos skills,
which is now part of Broadcom, and some of the team from there have gone on to form Icera,
a chip company working on mobile data. Independent start-ups include Elixent (now part of
Matsushita), Microcosm (now part of Conexant) and, in nearby Bath, picoChip building
massively parallel arrays, with wireless as a target.
South Wales has had a succession of companies setting up manufacturing plants around
Newport, but has suffered from the movement to off-shore manufacturing, as to a certain
extent has Colorado Springs.
In Colorado Springs, Simtek was a direct descendant, founded by Dick Petritz to
concentrate on memory after he left Inmos. Microtronix, initially specialising in
ferroelectrics, was another descendant, which in turn spun off Cova Technologies, Celis
Semiconductor, now concentrating on RFID and Albido.
Ramtron, another ferroelectric memory company was started in Colorado Springs recruiting a
significant number of Inmos people. Other companies that have been active in
semiconductors in the Colorado Springs area include Atmel, Micron, Mostek, United
Technologies, Honeywell and Intel, amongst others.
The roll call of major companies where Inmos alumni are in senior positions is large, as
perhaps it should be, as Inmos was able to be very selective in recruitment. There are
also many smaller consultancies working in the technology industries, offering such
services as audio newsletters, financial consultancy, marketing, PR, or design services
for semiconductors or systems. More specialist companies include Asset Recovery
International, which was founded on the experience of selling the manufacturing equipment
in the Colorado Springs fab, and Taeus, which helps companies with intellectual property
The transputer was welcomed in space applications, since an array of transputers could
provide the very high level of redundancy that space activities need. With the long life
of these projects, transputers are still in service today. For example, SOHO, the Solar
& Heliospheric Observatory (sohowww.nascom.nasa.gov), a joint European Space Agency
and NASA satellite, is sending back images of the sun using a transputer network.
The point-to-point technology to link transputers was formalised in the IEEE 1355
standard. This was further developed under the ESA into SpaceWire, which is now designed
into a number of space missions under development in Europe, the USA and Japan. A key
player in developing SpaceWire was Paul Walker from the transputer team whose company,
4Links, is now selling SpaceWire test equipment.
Another, less direct, influence can be seen in the HyperTransport standard for
chip-to-chip and board-to-board communication, which is also point-to-point and was
influenced, in part, by Inmos/Meiko veteran, Gerry Talbot.
While, as we have seen, the transputer was not a lasting commercial success, it was very
attractive in academic circles: a lot of doctoral theses were written in the late 1980s
and early 1990s around the transputer and occam. And many of those doctoral candidates are
in senior technical positions in a range of electronics companies, comfortable with the
idea that parallel processing is a practicable technology. Analyst Gary Smith of Gary
Smith EDA says of parallel processing: In this area people talk almost with
reverence about the transputer.
There is still considerable research going on in the CSP field, with the WoTUG forum
providing a focus for developments in CSP, including a Java implementation of CSP and an
annual conference. The recent growth in multicore processors, however, doesnt echo
the philosophy behind the Inmos approach. Where Inmos developed processor and programming
tools in tandem, with both chip and software using the same CSP model, the multicore
approach takes existing processor architectures and tries to impose parallelism on to it.
Iann Barron has said recently, Intel has hit the wall with the quad core. All they
are doing is multi-threading on several processors rather than just one; there isnt
enough inherent parallelism in Windows and current user applications to keep even four
processors usefully busy. He says that there is no magic formula to allow developers
to shoehorn large applications straight into parallel processing. Instead, as applications
are extended, new features should be implemented for parallelism, with those areas that
lend themselves most easily to parallelism, for example graphics rendering, being
reimplemented over time.
There are approaches to higher performance that are more closely aligned to the Inmos
approach: a schematic of Cradle Technologies multiple DSP engines on a single chip
looks very like an early schematic for the use of multiple transputers at a board level.
And ClearSpeed has 96 processing engines on a single die to produce the power of some
supercomputers when Inmos was founded. While Inmos failed in persuading most people that
it was possible to create parallel processing systems that are easy to programme, the
ideas are refusing to die. As the demand for more and more performance continues, it will
be interesting to see the Inmos ideas re-invented with new names. ¦
XMOS Keeping the Faith
Software Defined Silicon (SDS) from XMOS is a reinterpretation of the transputer ideas for
the 21st century.
David May, CTO of XMOS, was the architect of the Inmos transputer and is currently
professor of computer science at Bristol University, where he has developed the two
elements of the XMOS SDS approach, silicon and a software design flow. SDS aims to provide
consumer electronics developers with silicon that has ASIC flexibility and prices ($1 per
chip) and is at least as easy to programme as an FPGA.
The silicon is an array of simple, event-driven processors, the XCores. Their
functionality is defined in the development system using XMOS C language (XC) which is
standard C with extensions to cover, for example, IO port definition, thread behaviour and
parallelism. The developer can define dynamically how the processor matches processing
resources to each task, balancing control processing, signal processing and IO. Standard
C/C++ is used for applications, allowing re-use of legacy code, and a soft IP library is
First silicon is in 90nm fabrication at TSMC. Later this year there will be more
information on the architecture and a beta release of the tool set, which also includes
compilers, a debugger and development boards. Formal release of tools and silicon is
planned for the first quarter of 2008.