The December 2022 issue of IEEE Spectrum is here!

Close bar

Chip Hall of Fame: Acorn Computers ARM1 Processor

Reading this on a smartphone? Then you’re using a direct descendant of this processor right now

2 min read
Photo of Acorn Computers ARM1 Processor

Acorn chipPhoto: Acorn Computers


Manufacturer: Acorn Computers

Category: Processors

Year: 1985

In the early 1980s, Acorn Computers was a small company with a big product. The firm, based in Cambridge, England, had sold over 1.5 million 8-bit BBC Micro desktop computers as part of the BBC’s national Computer Literacy Project. It was now time to design a new computer. Unsatisfied with the processors then available on the market, the Acorn engineers decided to make the leap to creating their own 32-bit microprocessor.

They called it the Acorn RISC Machine, or ARM. RISC, which stood for reduced-instruction-set computer, was an approach to designing processors that traded more complex machine code for higher efficiency. The engineers knew it wouldn’t be easy; in fact, they half expected they’d encounter an insurmountable design hurdle and have to scrap the whole project. “The team was so small that every design decision had to favor simplicity—or we’d never finish it!” says codesigner Steve Furber, now a computer engineering professor at the University of Manchester. In the end, the simplicity made all the difference. The ARM was small, low power, and easy to program. Sophie Wilson, who designed the instruction set, still remembers when they first tested the chip in a computer. “We did ‘PRINT PI’ at the prompt, and it gave the right answer,” she says. “We cracked open the bottles of champagne.” In 1990, Acorn spun off its ARM division, and the ARM architecture went on to become the dominant 32-bit processor for embedded application. More than 10 billion ARM cores have been used in all sorts of gadgetry, including one of Apple’s most humiliating flops, the Newton handheld, and one of its most glittering successes, the iPhone. Indeed, ARM chips are now found in more than 95 percent of the world’s smartphones.

Photo: Steve Furber/Acorn Computers

One of the earliest sketches of the ARM1’s architecture.

The Conversation (0)

How Ted Hoff Invented the First Microprocessor

Hoff thought designing 12 custom chips for a calculator was crazy, so he created the Intel 4004

14 min read
How Ted Hoff Invented the First Microprocessor

The rays of the rising sun have barely reached the foothills of Silicon Valley, but Marcian E. (Ted) Hoff Jr. is already up to his elbows in electronic parts, digging through stacks of dusty circuit boards. This is the monthly flea market at Foothill College, and he rarely misses it.

Ted Hoff is part of electronics industry legend. While a research manager at Intel Corp., then based in Mountain View, he realized that silicon technology had advanced to the point that, with careful engineering, a complete central processor could fit on a chip. Teaming up with Stanley Mazor and Federico Faggin, he created the first commercial microprocessor, the Intel 4004.

Keep Reading ↓Show less