ARM has launched a new processor architecture specifically for multiprocessors that can put several processors in the space of a single high performance core.

The Cortex A9 is aimed at consumer and low power applications, such as next generation mobile phones. Two cores running at 500MHz can be used in the same area as one running at 1GHz, giving the same performance but with 40 per cent less power at 65nm, said John Goodacre, the multiprocessor programme manager at ARM.

This comes from both the design of the core and the use of less aggressive synthesis as less area is used as less speed is needed.

Cortex core

The Cortex A9 core can provide the same performance as the previous Cortex A8 core, but has a very different structure that is optimised for multiprocessing. It uses an 8 stage superscalar core that issues two instructions per cycle, although the pipeline is configured in real time so that simple instructions pass through in five stages.

This dynamic pipeline also issues more load/store instructions, up to a total of four, to make sure the pipeline stays full.

ARM has implemented out-of-order execution for the first time, using the configurable pipeline to avoid having large instruction buffers to match up data and instructions at the end.

This is not aimed at massively parallel systems, but for system controllers in set-top boxes and portable media players.

"We expect up to four cores being used, and that's what our customers are looking at," said Goodacre. This could provide up to 8000DMIPS in performance. "We see this as an upgrade from the ARM9 and ARM11 to provide a choice of a single core and a roadmap to multiprocessing, rather than an upgrade to the A8," he said.

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