Sophie Wilson by @SebastianNavasF

Sophie Wilson — Architect of the Modern World

Regardless of the technology you are using to read this post, you need to know that its processor was early designed by a trans woman named Sophie Wilson. The ARM microprocessor core is now used in thousands of different products, including smartphones, tablets, gaming consoles and broadband routers. Because of this, the British engineer Sophie Wilson is said to be one of the architects of the modern world.

Over a summer holiday and while she was still a student, Wilson designed and constructed a prototype computer. Her summer project later became the basis for Acorn’s first computer called Acorn System 1, launched in 1979 by the newly established Acorn Computers company. System 1 was cheap and came as a kit that the user would assemble by themself with a manual, but even as its following versions, it was far from being a popular item.

They became well-known after the BBC Broadcaster’s Literacy Program payed Sophie and her co-workers to build the BBC Micro, seeking to bring computers to kids at school in a sort of old-school “One Laptop per Child” project. The BBC Micro was a real success but the processor behind that computer, an 8-bit 6502 that ran at 2MHz, was far from satisfactory. So, in 1983 they decided to build their own CPU.


Some 35 years ago, the Acorn RISC Machine or ARM was built. Steve Furber focused on the hardware architecture and Sophie Wilson designed the instruction set for one of the first RISC processor. The ARM1 was a tiny, low-power, efficient 32-bit CPU with about 25,000 transistors using a 3 micron process. This was truly a milestone in British engineering.

Visual ARM simulator

With the 6502 processor the fastest operation was done in two clock cycles (one microsecond). With the ARM1 32-bit operations could be done much quicker. But, the ARM1 didn’t have less instructions than the 6502, it was the complexity on how the instructions were implemented that was reduced.

There wasn’t a unique microprocessor company in the world, there were a number of them producing RISC powered machines and there was a lot of creativity in the market. But everybody was concentrating on high execution throughputs by increasing the complexity of instructions that tended to slow down processors. With high-level design choices and assigning a limited set of simple instructions Sophie made them perform better with less power and at a lower price.

The Legacy

The ARM1 was quickly followed by the ARM2 (used to launch Acorn’s Archimedes family of computers), ARM3, ARM6 and so on. ARM became the most successful licensed computer core up to present. Today you can find Cortex-A ARM processors in thousands of different electronics products, powering multiple applications such as industrial equipment, wireless infrastructure, hard disk drives, smart phones, tablets, readers, smart TVs, game consoles and smart appliances. The ARM microprocessor is used in almost everything you hold in your hands nowadays.

The story of Sophie Wilson, shows us the story of a person that understands tradeoffs, something crucial in software development. She figured out the need to simplify the instruction set, because among other things, they had a small team for designing their chip. Good team work and a keen eye for choosing the right tradeoffs, let her change the CPU world forever.

Plot in the wall of ARM1 and Sophie Wilson bearing a plot to the same scale of an ARM Cortex-M0+

Advent Calendar — Help us make it a book!

From December 1st until December 24th we plan to release one article each day, highlighting the life of one of the many women that have made today’s computing industry as amazing as it is: From early compilers to computer games, from chip design to distributed systems, we will revisit the lives of these pioneers.

Each article will come with an amazing illustration by @SebastianNavasF

If you want to see these series to become a book with expanded articles and even more illustrations by Sebastián, then subscribe to our newsletter below.



A Computer of One’s Own

Pioneers of the Computing Age

Florencia Grattarola

Written by

Uruguayan PhD student in Evolution & Ecology in the UK.

A Computer of One’s Own

Pioneers of the Computing Age

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