Big Blue turns green with power down chips

IBM is developing an additional deep-sleep mode for its Power processors, enabling them to only draw a nominal current when idling in "Winkle" mode.

Power7 chips currently have two energy-saving modes: nap and sleep. These are selected according to the workload and how much latency an application can tolerate before it fails.

Nap mode only cuts the processor voltage by 15 per cent, but the heavy sleep mode would bring this down to an 85 per cent saving. This level is designated by IBM at a point on the energy reduction curve called the RV Winkle Power gate.

The trade off is in latency. From nap mode, the processor comes back almost instantly. From sleep, this stretches to two milliseconds, but the new level will take up to ten times as long to recover.

The announcement was made by IBM engineer Michael Floyd during a presentation at the Hot Chips conference held at Stanford University, California.

He called his announcement "a little teaser for future chips" and did not specify a roadmap for the Winkle chips. The current Power7 chips have the RV Winkle Power gate but whether this can be easily accessed is not known.

Power 8 chips will be quite a way off, so it could be IBM plans an intermediate release of Power7 processors.

Power chips have always had sleep modes and Intel has said its Xeon 5600 cores can be powered down almost completely.