Today Is the 40th Anniversary of the BBC Micro...and the Ancestry of Arm

Today is the 40th anniversary of the release of the BBC Micro. It was released on 1st December 1981. It was designed and manufactured by Acorn Computer in Cambridge. The BBC is the British Broadcasting Corporation, which launched a computer literacy project commissioned by the computers that went along with it. Although people usually say "BBC Micro" they usually mean the "model B" which came in several versions depending on how much memory it had. The aim was to put a computer in every school in Britain.

The BBC put out a call for bids for the project and Acorn Computers won with a computer called the Proton, which was subsequently renamed. It was used by most schools in the UK despite its comparatively high cost (the model A cost £235 and the model B cost £335 in 1981 dollars). By comparison, the main competition was Sinclair's ZX81 which cost £49.45 in kit form or £69.95 assembled. Acorn had an early computer called Atom and was already working on a successor machine that would become Proton. It had better graphics and a faster (!) 2MHZ MOS technology 6502 microprocessor, but it was only at the design stage at the time so the Acorn team just had a week to build a working prototype from the designs. It was a surprise to the BBC in many ways, who expected a Z80-based machine running CP/M, not a 6502-based machine running Acorn's proprietary operating system Acorn MOS.

The BBC made a program (a TV program, that is) called The Computer Programme to go along with the project. Over time, 1.5 million BBC Micros were sold.

Sir Clive Sinclair

As it happens, Sir Clive Sinclair passed away recently, and Simon Segars, Arm's CEO, gave a tribute to him and his computers in his opening keynote at the recent Arm event. You can read about that in my post Simon Segars: Arm DevSummit Keynote...and Sir Clive Sinclair.

The BBC made a docudrama about the rivalry between Acorn and Sinclair. As the abstract for the video says:

The rivalry comes to a head when the BBC announces their Computer Literacy Project, with the stated aim of putting a micro in every school in Britain. When Acorn wins the contract, Sinclair is furious, and determines to outsell the BBC Micro with his ZX Spectrum computer. Home computing arrives in Britain in a big way, but is the country big enough for both men?

If you have any interest in the early history of computers, I recommend watching (it's 1 hour 20 minutes long). Some of the actors look disturbingly like the real people did back forty years ago.

Arm

When Simon Segars gave his Arm DevSummit keynote, he told the story that the first computer he programmed was a Sinclair ZX81. He didn't own one, since at £70 he couldn't afford one. Then, when the Computer Literacy Project started, Simon finally got his hands on a BBC Micro. I don't know if he purchased one or if it was at school, but found his passion and would go on to study engineering at Sussex and Manchester.

You may already know the story of Arm. Steve Furber and Sophie Wilson (and some others) decided that there were no good choices of microprocessor for the next product from Acorn Computers. So they decided to design their own. In some ways, looking back, this was an insane decision at the time, and might have been a disastrous case of NIH, not-invented-here. That was 1985 and the first computer was the Arm1. The Arm1 and Arm2 were just processors but by the time of the Arm3 there was room for a cache too. In a weird bit of coincidence, I installed the VLSI Technology EDA software that was used to design the first Arm processors, and VLSI manufactured them. That was on two Apollo workstations. But Apollo hadn't yet shipped the computers to Acorn in Cambridge so I had to go to some industrial estate in North London and install the software before the workstations shipped. Amazingly, everything went smoothly.

When Apple decided to create the Newton, they came to the conclusion that the best processor was Arm, since it hit the sweet spot of high-performance but low-power, important for any hand-held device. However, Apple didn't want to depend on a processor that we buried in a struggling English computer company, so they forced Acorn (by then owned by Italian company Olivetti) to spin it out. I think it ended up with 45% ownership by Apple (who put in the initial funding), 45% by Olivetti (who owned the Arm architecture), and 10% by VLSI Technology who provided all the design tools necessary to design the chips for equity.

The Newton was too early in many ways, and even with a good Arm processor, it was underpowered. It was eventually discontinued after 5 years. In fact, given how successful Arm is today, it is hard to appreciate just how unsuccessful it was in the early days. As Tudor Brown said when he stepped down as President of Arm and left the company:

All of ARM's early products failed commercially. There's a long list of them: the Acorn machine, the Apple Newton, the 3DO multi-player. There were a whole bunch of things like that.

You can read a bit more history from my 2015 piece just after I rejoined Cadence, Happy 25th Birthday, ARM.

Going Mobile

When did Arm's fortune's look up? When Nokia and Texas Instruments decided to use the Arm 7 in its cellphones. This required adapting the instruction set since the code density was poor. So in a very short time, the 16-bit "thumb" instruction set was added to create the ARM7TDMI. You can read about that in my post The Design that Made ARM.  The ARM7TDMI would become the standard processor for early generations of mobile, with over 30 billion of them shipped. Simon Segars told me that by unit volume it is probably the most successful microprocessor ever, at least 6 years ago.

Going back to pretty much where we came in, the lead designer for the ARM7TDMI and its eventual project lead was Simon Segars. Of course, Arm would be acquired by Japanese company Softbank, and then NVIDIA is in the process of acquiring the company from them, although it seems to be tied up in various regulatory issues for now. So watch this space.

But it all started 40 years ago today with the BBC Micro.

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