ARM updates chip instructions

The Cambridge, England-based chip designer unveiled on Monday a set of processor instructions designed to help cell phones run faster and consume less energy.

ARM's Thumb 2 instructions update the company's original Thumb instructions, a subset of commands inside the overall ARM architecture, the basic architecture behind the chips running most cell phones on the market today.

Software code written to take advantage of the Thumb 2 instructions is generally 26 percent shorter than the code written for the rest of the ARM chip, said Richard Phelan, embedded CPU (computer processing unit) manager at ARM. As a result, Phelan said, these tasks can be completed in less time, which means they consume less battery life.

Thumb 2 can't do everything. The technology only handles 16-bit instructions. The rest of the ARM architecture is designed for more complex, 32-bit functions. Still, having an express lane of sorts for some functions gives cell phone designers and software developers a way to use the limited amount of memory inside of cell phones more efficiently.

"We've just varied the instruction size of some instructions to make them smaller," Phelan said, noting that mixing 16-bit and 32-bit instructions on a single RISC chip like the ARM is a bit unusual. "In purist terms, RISC processors use a single instruction size." RISC is a computer architecture that reduces chip complexity by using simpler instructions.

Thumb 2, which was announced at the Embedded Processor Forum taking place in San Jose, Calif., this week, updates the original Thumb instructions, which the company came out with in 1995.

The Thumb 2 instructions will appear in an update to the ARM architecture the company will unveil later in the Fall and will be the major change found in the new version of the architecture. Products featuring chips built around the new architecture will likely be seen on store shelves 18 months later.

The time gap in part is dictated by ARM's business model. The company designs chips but doesn't make them. Instead, it licenses its blueprints and intellectual property to Motorola, Intel and others, who in turn manufacture chips which get sold to cell phone makers.