ARM History, Part 1: Building the First Chip

ARM History, Part 1: Building the First Chip

Orrich Lawson/Getty Images

It was 1983 and Acorn Computers was on top of the world. Unfortunately, trouble was just around the corner.

This small British company was famous for winning a contract with the British Broadcasting Corporation to build computers for national television programs. The company’s sales of his BBC Micro soared to over 1.2 million units.

Magazine advertisement for BBC Micro.the catchphrase is
Expanding / Magazine advertisement for BBC Micro. The catchphrase is “The Shape of Things to Come”.

However, the world of personal computers was changing. The market for inexpensive 8-bit microprocessors that parents bought to help their kids with homework was becoming saturated. And new machines across the pond, such as the IBM PC and the upcoming Apple Macintosh, promised far greater power and ease of use. Acorn needed a way to compete, but didn’t have much money for research and development.

seeds of ideas

Sophie Wilson, one of the BBC Micro’s designers, anticipated this problem. She added slots called “tubes” that could be connected to more powerful central processing units. A slotted CPU can hijack a computer, freeing up her original 6502 chip for other tasks.

But which processor should you choose? Wilson and co-designer Steve Furber looked at various 16-bit options, including Intel’s 80286, National Semiconductor’s 32016, and Motorola’s 68000, and were completely satisfied. Nothing could be done.

286, 32016, and 68000 CPUs (roughly scaling).
Expanding / 286, 32016, and 68000 CPUs (roughly scaling).


In a subsequent interview with the Computing History Museum, Wilson explained: The first thing they didn’t do was make poor use of the memory system. The second thing he didn’t do was they weren’t fast. They were hard to use. We were used to programming the 6502 in machine language, but hoped it would reach a level of power that would allow him to achieve the same type of results if written in a higher level language. “

But what were the alternatives? Could a little acorn even conceive of building its own CPU from scratch? To find out, Wilson and Farber traveled to the National Semiconductor factory in Israel. They saw hundreds of engineers and tons of expensive equipment. This confirmed their suspicions that such work might be beyond them.

Then we visited the Western Design Center in Mesa, Arizona. This company had manufactured his beloved 6502 and designed his 65C618, a 16-bit successor. Wilson and Farber found nothing more than a “suburban bungalow” with a few engineers and some students making diagrams using old Apple computers and sticky tape.[computersandbitsofstickytape[computersandbitsofstickytape

Western Design Center in 2022, according to Google. It may be the same bungalow!
Expanding / Western Design Center in 2022, according to Google. It may be the same bungalow!

Suddenly it seemed that it might be possible to build your own CPU. Wilson and Furber’s small team had previously created custom his chips, such as graphics and input/output chips for the BBC Micro. However, these designs are simpler and have fewer components than CPUs.

Despite the challenges, Acorn’s senior management supported their efforts. In fact, they were more than just support. Acorn co-founder Herman Hauser, a Ph.D. in physics, provided the team with a copy of his IBM research paper describing his new type of CPU, which is more powerful. It was called his RISC, which stands for “Reduced Instruction Set Computing”.

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