The Birth of ARM: From Acorn's BBC Micro to a Global RISC Powerhouse

In the early 1980s, Acorn (originally called Acron) received a contract from the BBC to develop a low‑cost microcomputer for UK schools. Under intense pressure, engineers Roger Wilson and Steve Furber built a prototype in just a week, impressing the BBC team and securing a multi‑million‑pound order for the BBC Micro.

After the success of the BBC Micro, Acorn explored more powerful CPUs. Dissatisfied with the complexity of existing processors such as Motorola’s 68K and National Semiconductor’s NS32016, they turned to the emerging RISC concept pioneered at Stanford and Berkeley, which promised higher performance with a simplified instruction set.

In 1985, Acorn launched the ARM (Acorn RISC Machine) project. Wilson designed the instruction set while Furber handled the circuit implementation. The first ARM chip, containing 25,000 transistors, was fabricated in April 1985 and ran a BASIC interpreter with virtually no power consumption, demonstrating the low‑energy advantage of RISC.

The small size and efficiency of the ARM core made it ideal for System‑on‑Chip (SoC) designs. In 1990, ARM spun out as an independent company, adopting a licensing model that allowed other manufacturers to integrate the ARM architecture into their products.

Apple’s early Newton tablet used an ARM processor, and after Steve Jobs’s return, ARM became the backbone of iPod, iPhone, and iPad, driving massive adoption. Today, ARM partners have shipped over 200 billion chips, making ARM the world’s most ubiquitous CPU architecture.

The story also notes the personal journey of Wilson, who transitioned to Sophie Wilson in 1994, continued contributing to ARM’s evolution, and later worked at Broadcom after Acorn’s acquisition.