Acorn Archimedes

The Acorn Archimedes arrived in 1987 with astonishing power. While competitors ran 8-bit and 16-bit processors, the Archimedes used a 32-bit ARM chip that Acorn designed themselves. The machine was years ahead technically—and commercially struggled because of it. But the ARM processor inside would eventually power billions of devices.

Fast facts

Manufacturer: Acorn Computers.
Released: June 1987.
CPU: ARM2 at 8 MHz (32-bit RISC).
RAM: 512KB to 4MB depending on model.
Graphics: 256 colours on screen, from a 4,096-colour palette.
Sound: 8 channels, each independently placed in the stereo image — generated by the video controller.
OS: Arthur, then RISC OS.
Price: £799-£1,399 depending on model.

Four chips, and an unusual division of labour

Acorn’s manual describes the machine as “the ARM chip set”, and the interesting part is what the three supporting chips do.

Chip	Job
ARM	32-bit data bus, 26-bit address bus, “giving a 64 MB uniform address space”
MEMC	memory control — and “all the critical system timing signals, including processor clocks”
VIDC	video and sound, both fetched from DRAM by DMA
IOC	input/output, and interrupt handling

Two of those entries are not where a reader would expect them.

The memory controller clocks the processor. MEMC generates the ARM’s clocks rather than receiving them. The CPU’s timing is a property of the memory system, which is the opposite arrangement to a machine where the processor runs at a fixed rate and the memory keeps up.

MEMC also carries a Logical to Physical Translator, mapping memory into a 32 MB logical address space “with three levels of protection”, which is what allowed RISC OS to do virtual memory and multi-tasking on a home machine in the 1980s.

The video chip makes the sound. VIDC “takes video data from memory under DMA control, serialises it and passes it through a colour look-up palette” — and on the same die “incorporates an exponential Digital to Analogue Converter (DAC) and stereo image table for the generation of high-quality sound from data in the DRAM”.

So both streams the machine plays continuously, picture and audio, come out of one chip pulling from the same DRAM. Eight sound channels, each with its own position in the stereo image, filtered for a 20 kHz sample rate — this is the Amiga’s trick of DMA-driven sampled audio, done by the video controller.

The palette is a detail worth having exactly: 13 bits wide, “offering a choice from 4096 colours or an external video source”. The 256 colours usually quoted for the Archimedes are how many can be on screen; 4,096 is what they are chosen from.

ARM: Acorn RISC Machine

Acorn designed their own processor:

RISC architecture: Simpler instructions, faster execution.
32-bit: When competitors used 8 and 16 bits.
Low power: Efficient design from the start.
In-house: Acorn controlled their destiny.

The ARM would outlive Acorn itself by decades.

Raw performance

The Archimedes was staggeringly fast:

MIPS rating: 4+ MIPS versus 1 MIPS for 68000 machines.
Graphics: Hardware could outperform Amiga in many tasks.
Sound: 8-channel DMA-driven audio.
I/O: Fast disc access, networking support.

Educational market

Like the BBC Micro before it, schools adopted Archimedes:

UK government education contracts.
RISC OS’s desktop interface suited classrooms.
Acorn’s educational software expertise.
Installed base in British schools.

Gaming potential

The hardware enabled impressive games:

Zarch/Virus: David Braben’s 3D landscape game.
Chocks Away: Flight combat.
Star Fighter 3000: Fast 3D action.
Cannon Fodder: Born on Archimedes.

Yet the small market limited commercial development.

Why it struggled commercially

Despite technical superiority:

Price: Expensive versus Amiga and ST.
Software library: Smaller than competitors.
Business market: PC compatibles dominated.
Timing: Arrived as 16-bit market peaked.

ARM’s independence

The processor’s importance grew:

ARM spun off as separate company (1990).
Licensed to other manufacturers.
Apple Newton used ARM (1993).
Mobile phones adopted ARM architecture.
Now powers most smartphones worldwide.

The Acorn legacy

Acorn faded, but ARM thrived:

Company restructured, renamed, eventually dissolved.
RISC OS continues via enthusiasts.
ARM Holdings became tech giant.
Acquired by SoftBank (2016), Nvidia bid failed (2022).

Legacy

The Archimedes proved British engineering could lead the world—even if British marketing couldn’t sell it. The ARM processor born in Cambridge now powers billions of devices. Every smartphone, most tablets, countless embedded systems run on Acorn’s architecture.

The ARM's birthplace