A look back at UK-based Acorn, which created Acorn RISC Machine (ARM), a RISC-based CPU, and in 1987, the first RISC-based PC, Acorn Archimedes
Jason Torchinsky / Ars Technica : Tweets: @padraig and @monkeydom Tweets: @padraig : We have ARM processors because in the early 80s, the British govt saw that computers would be important, invested in them with a contract to invent & produce a computer which they then bought for all their schools. https://twitter.com/... @monkeydom : I spent the first decade of my serious computer life with Acorn. The Archimedes, RiscOS and later the RiscPC spoiled me for life. Hard to put in words how far ahead of the time they were. Sadly a lack of style and marketing ended Acorn way ahead of time. https://twitter.com/...
Context & Ripple Effects
This retrospective lands at a moment when Acorn's 1985 ARM1 — 25,000 transistors, per Ken Shirriff's die-level comparison against Apple's M1 — suddenly matters commercially again: Kuo had flagged Apple's move off Intel months earlier, and the M1 shipped weeks before this piece ran.
The through-line is institutional as much as technical. A British government contract put Acorn machines into schools; decades later Arm holds a minority stake in Raspberry Pi, whose every SoC runs an ARM core, and Mercury Research puts ARM at roughly 8% of PC chips.
First-order effects
- Apple's Intel-to-ARM Mac transition, presaged by Kuo's early-2020 prediction, makes Acorn's architecture the engine of a flagship PC line for the first time since the Archimedes.
- Arm's minority stake in Raspberry Pi extends a partnership dating to 2008 that has kept ARM CPUs in every Raspberry Pi SoC — education hardware, the same constituency the original government contract seeded.
Second-order effects
- Mercury Research's finding that ARM reached about 8% of PC chips in Q3 2021, up from 2% a year earlier, pressures x86 incumbents to compete on performance-per-watt rather than clock speed alone.
- RISC's widening adoption sets up a licensing contest inside the RISC camp itself: Wired's account of the Arm-versus-RISC-V war shows the heirs of Acorn's design now fighting each other for the ecosystem Acorn created.
Third-order effects
- If RISC keeps displacing CISC — the pattern Wired documents as the 'RISCites' beating the CISCites — the durable shift is toward licensable instruction-set architectures, weakening the single-vendor dominance US chip companies have held.
- The Acorn story suggests state procurement can seed architectures that outlive the company: a schools contract produced the ISA now embedded in phones, Macs, and Pi boards, a template other governments eyeing sovereign silicon will study.
The trend: Computing's center of gravity is shifting from CISC x86 to RISC architectures descended from Acorn's work, with Arm and RISC-V now competing over that inheritance.