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A brief history of ARM, part 1: Building the initial chip

A history of ARM, part 1: Building the first chip

Aurich Lawson / Getty Images

It had been 1983, and Acorn Computers was along with the planet. Unfortunately, trouble was coming.

The tiny UK company was famous for winning a contract with the British Broadcasting Corporation to make a computer for a national tv program. Sales of its BBC Micro were skyrocketing and on pace to exceed 1.2 million units.

A magazine ad for the BBC Micro. The tagline was

Enlarge / A magazine ad for the BBC Micro. The tagline was “THE FORM of What to Come.”

However the world of computers was changing. The marketplace for cheap 8-bit micros that parents would buy to help kids making use of their homework was becoming saturated. And new machines from over the pond, just like the IBM PC and the upcoming Apple Macintosh, promised a lot more power and simplicity. Acorn needed a method to compete, nonetheless it didnt have much money for research and development.

A seed of a concept

Sophie Wilson, among the designers of the BBC Micro, had anticipated this issue. She had added a slot called the Tube which could connect to a far more powerful central processing unit. A slotted CPU could dominate the computer, leaving its original 6502 chip free for other tasks.

But what processor should she choose? Wilson and co-designer Steve Furber considered various 16-bit options, such as for example Intels 80286, National Semiconductors 32016, and Motorolas 68000. But none were completely satisfactory.

The 286, 32016, and 68000 CPUs, roughly to scale.

Enlarge / The 286, 32016, and 68000 CPUs, roughly to scale.

Wikipedia

In a laterinterview with the Computing History Museum, Wilson explained, We’re able to see what each one of these processors did and what they didnt do. Therefore the very first thing they didnt do was they didnt make good usage of the memory system. The next thing they didnt do was they werent fast; they werent simple to use. We were used to programming the 6502 in the device code, and we rather hoped that people could easily get to an electrical level in a way that in the event that you wrote in an increased level language you can achieve exactly the same forms of results.

But that which was the choice? Was it even thinkable for tiny Acorn to create its CPU from scratch? To discover, Wilson and Furber took a vacation to National Semiconductors factory in Israel. They saw a huge selection of engineers and an enormous quantity of expensive equipment. This confirmed their suspicions that this type of task may be beyond them.

They visited the Western Design Center in Mesa, Arizona. The corporation was making the beloved 6502 and designing a 16-bit successor, the 65C618. Wilson and Furber found bit more when compared to a bungalow in a suburb with several engineers plus some students making diagrams using old Apple II computers and items of sticky tape.

The Western Design Center in 2022, according to Google. It might even be the same bungalow!

Enlarge / The Western Design Center in 2022, in accordance with Google. It could even function as same bungalow!

Suddenly, making their very own CPU appeared like it may be possible. Wilson and Furbers small team had built custom chips before, just like the graphics and input/output chips for the BBC Micro. But those designs were simpler and had fewer components when compared to a CPU.

Regardless of the challenges, upper management at Acorn supported their efforts. Actually, they went beyond mere support. Acorn co-founder Hermann Hauser, who had a Ph.D. in Physics, gave the team copies of IBM research papers describing a fresh and much more powerful kind of CPU. It had been called RISC, which stood for “reduced instruction set computing.”

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