IN THE EARLY EIGHTIES the Cambridge computer company Acorn sent engineers Steve Furber and Sophie Wilson to the US to check out a processor being developed by Motorola.
They were astonished to find the development work being done by "bunch of people working in a bungalow and ... employing high-school kids to do circuit design."
Furber, now ICL Professor of Computer Engineering at Manchester University, recalled, "We came away saying that if they could design a processor, then so could we."
Acorn, which was riding high from the success of the BBC Micro computer, had been looking for a processor to power a machine capable of competing with the new IBM PC. The two engineers decided that the best way to get the processor the company wanted was to design one in-house.
Furber worked on the hardware; Wilson, now chief architect at Broadcom's DSL business unit, wrote the instruction set. Fortuitously, as it turned out, they had to save on cooling costs by keeping the power consumption below 1watt, an aim pursued so assiduously that the new processor drew only a tenth of that.
A version of the chip was used on Acorn's Archimedes computer, which though innovative and much loved did not exactly sweep the world. But the processor architecture did, after being promoted and developed by an Acorn spin-off called Advanced Risc Machines.
ARM processor cores, thanks largely to their low power drain, now outnumber by far those using the PC's x86 architecture. Twelve billion of them have been used in mobile devices alone, 2.5 billion of them last year; they are in an estimated 99 out of 100 mobile phones, which use an average of 2.2 ARM cores each.
ARM processors range from embedded controllers the size of a pinhead to multi-core systems-on-a-chip(SoCs) offering PC-class performance at a fraction of the power drain. These are all made by licensee companies who surround ARM cores with peripheral functionality such as graphics. The latest SoCs support full-HD 1080p graphics at 30 frames per second, as well as Adobe Flash 10.1 running under Android. They include:
These three are all built round a dual-core ARM Cortex-A9 MPCore processor - the same processor rumoured to be at the heart of Apple's iPad, though it can have four cores. Two other powerful SoCs come from companies that licence only the ARM instruction set for use in their own core designs:
Dual-cores have too much processing power for many uses. Amazon's Kindle 2 and the Sony eBook reader have relatively modest processing needs and use single-core i-MX SoCs from Freescale. This company showed a neat reference design for a tablet using its Cortex A8-based i.MX515 SoC, and with a keyboard doubling as a docking station (pictured).
The big question is whether all this computing power is going to burst out of smartphones and into larger formats, putting them into direct competition with thicker and thirstier Intel-based netbooks and laptops. Most of the tablets we have seen so far have been not-for-sale concept and reference designs.
Bob Morris, director of mobile computing at ARM, agrees that many manufacturers have been waiting to see what Apple (an early investor in ARM) comes up with in its iPad. He points out that people are using these smaller formats in a different way from laptops. The new devices place more of a focus on browsers and people use them for consuming multimedia media, checking their email, social networking rather than using the office applications that are the mainstay of PCs.
These tasks are well suited to the kind of interface Apple introduced on the iPhone, though it remains to be seen how well this will work in a larger format.
The fact is that ARM-device users can easily have the best of both worlds. Office applications can be readily used online, and a simple client software module can allow an ARM-based tablet to act as an untethered front end to an office or home PC over a Wifi link.
Microsoft demonstrated this eight years ago with its design for what it called a Smart Display, which doubled as a small supplementary desktop monitor and portable Windows terminal. It worked very well but the project quickly failed because products that hit the market were ludicrously overpriced.
But even this setup is a little too PC-centric for the way the technology is heading. Morris points out that Samsung makes ARM-based SoCs and their support for HD video means they could as easily drive a television as a smartphone screen. Samsung also make televisions.
So your TV can double as a computer, or a front end for another computer, or to screen content streamed from your mobile. It is evolving into a general purpose screen that can take advantage of your smart mobile's HD graphics (which are indistinguishable from standard definition on any screen smaller than 27-inch, according to the BBC).
Arguably it is still too early for tablets to succeed. To reach their potential they need better screens, better screen textures, truly ubiquitous affordable connectivity, and (crucially) better input facilities.
But the processors are getting there. These new SoCs are wonderful 21st-century mobile computing engines and even vaunted Apple appears to be underusing them, restricting multitasking and shunning Adobe's Flash. Apple's multi-touch operating system may be cool, but with rivals like Android and even Windows Mobile 7 it is no longer exclusively so
These SoCs are to the emerging mobile era what the PC platform was to the age of the desktop, and manufacturers with bottle and imagination could use them to consign Apple with its elegant walled garden of lock-ins to the cosy niche where it belongs. µ