Feeds

ARM creators Sophie Wilson and Steve Furber

Part Two: the accidental chip

The Power of One Infographic

Call to ARMs

The first ARM used 25,000 transistors. "It was a really small, simple piece of design," says Furber.

Today one of the most significant features of the ARM family is its low power consumption. But that hadn't been an initial goal, according to Furber. “We designed the ARM for an Acorn desktop product, where power isn't of primary importance. But it had to be cheap. Cheap meant it had to go in a plastic package, plastic packages have a fairly high thermal resistance, so we had to bring it in under 1W.”

The orginal ARM chip at 3µm

The original 3µm ARM chip

The power test tools they were using were unreliable and approximate, but good enough to ensure this rule of thumb power requirement. When the first test chips came back from the lab on the 26 April 1985, Furber plugged one into a development board, and was happy to see it working perfectly first time.

Deeply puzzling, though, was the reading on the multimeter connected in series with the power supply. The needle was at zero: the processor seemed to be consuming no power whatsoever.

As Wilson tells it: “The development board plugged the chip into had a fault: there was no current being sent down the power supply lines at all. The processor was actually running on leakage from the logic circuits. So the low-power big thing that the ARM is most valued for today, the reason that it's on all your mobile phones, was a complete accident."

Wilson had, it turned out, designed a powerful 32-bit processor that consumed no more than a tenth of a Watt.

Steve Furber's ARM SoC Architecture

From the horse's mouth...

“Running on leakage” also happened to be an appropriate description of Acorn outside the lab. To staunch the haemorrhaging finances, Italian computer manufacturer Olivetti stepped in with an initial cash injection in February 1985. By the end of the year, Olivetti had taken a controlling interest, effectively buying the company.

“Olivetti wasn't told about the ARM when they bought Acorn,” Steve Furber remembers. When they found out, he says, “they didn't know what to do with it”. Wilson and Furber did, and were able to push through the ARM’s initial commercial appearance in the ARM Development System, a specialist add-on to BBC Micro costing £4500.

Top three mobile application threats

More from The Register

next story
Child diagnosed as allergic to iPad
Apple's fondleslab is the tablet dermatitis sufferers won't want to take
Microsoft takes on Chromebook with low-cost Windows laptops
Redmond's chief salesman: We're taking 'hard' decisions
For Lenovo US, 8-inch Windows tablets are DEAD – long live 8-inch Windows tablets
Reports it's killing off smaller slabs are greatly exaggerated
Seventh-gen SPARC silicon will accelerate Oracle databases
Uncle Larry's mutually-optimised stack to become clearer in August
EU dons gloves, pokes Google's deals with Android mobe makers
El Reg cops a squint at investigatory letters
Big Blue Apple: IBM to sell iPads, iPhones to enterprises
iOS/2 gear loaded with apps for big biz ... uh oh BlackBerry
prev story

Whitepapers

Top three mobile application threats
Prevent sensitive data leakage over insecure channels or stolen mobile devices.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.
Mobile application security vulnerability report
The alarming realities regarding the sheer number of applications vulnerable to attack, and the most common and easily addressable vulnerability errors.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.