Wishing the ARM processor a happy 30th birthday

Today, 26th April, 2015 isn’t just the morning after this year’s Wakefield Show; it is also 30 years to the day since the very first ARM1 processor was produced, powered up – and worked!

The story of the new processor goes back a little further than 26th April, 1985, and  started when Acorn were looking for a suitable replacement for the MOS 6502 CPU, which at that point they were using in the BBC Microcomputer range. While considering alternative processors that could be used, Acorn visited the Western Design Center in Arizona where Bill Mensch, formerly an employee of MOS Technology Inc., was working on updates to the 8-bit processor. Upon seeing that WDC was effectively a single-person operation, Steve Furber and Sophie Wilson realised that Acorn should be able to design their own chip, and that’s what they set about doing.

The project to design a new processor – to be called the Acorn RISC Machine – officially started in October, 1983. Sophie Wilson designed the instruction set, and a simulation of the processor was developed in BBC BASIC running on a BBC Micro with a 6502 second processor – in just over 800 lines of code. Steve Furber was the lead on the hardware design team and, with VLSI Technologies fabricating the design, the first piece of silicon was delivered on 26th April, 1985.

At 3pm on the same day, that same first piece of silicon was successfully brought to life: The ARM processor was born.

The first version of the ARM – a 3.5micron, 32-bit processor with a 26-bit address bus and fewer than 25,000 transistors – was used in a (non-commercial) second processor system for the BBC Micro via its Tube interface, called the ARM Evaluation System. Its purpose was to allow the designers to – as its name suggests – test and evaluate the system, without the need to design and build a whole computer around it.

For RISC OS users, the most significant result of the development of the ARM processor came in June 1987, with the release of the first of the Archimedes computer range. The operating system at that point was Arthur – which, possibly apocryphally, is said to stand for “A RISC Operating System by Thursday” and indicates that it may have been developed rather quickly. Arthur was soon to be replaced with a more polished RISC OS, which – along with newer versions of the processor – was to be used in Acorn’s computers right up to the RiscPC 2, aka Phoebe, which was sadly cancelled in 1998, shortly before Acorn itself closed down.

The development and story of the ARM itself doesn’t end with Acorn, however – the processor’s name was changed from Acorn RISC Machine into Advanced RISC Machine in 1990 when a new company, Advanced RISC Machines Ltd was formed to further develop the processor. Going from strength to strength, Advanced RISC Machines Ltd became ARM Ltd in 1998, when ARM Holdings plc was floated on the stock market, and today the ARM processor is so ubiquitous that there are now more of them in use than there are people on Earth, and (in various incarnations) they can be found in everything from household appliances to mobile phones and tablets.

And, lest we forget, they are still used in computers that run RISC OS!


Sadly, this article hasn’t had the time or attention given to it that I would have liked. It was written the night before the 2015 Wakefield Show, two days before the anniversary. As such it lacks any real depth or detail – but despite the lack of time to write something more detailed, I couldn’t let the 30th anniversary of the birth of the ARM processor go by without at least some kind of mention.

Hopefully, despite being written in such a last-minute, rushed manner, no major lapses in accuracy have crept in!

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