CSR is working with Intel to reduce power by up to a Watt when integrating its Bluetooth device into a laptop PC. 

As part of the collaboration, CSR has developed new Bluetooth firmware and complementary Windows software which implements an Intel-developed power-saving technique called USB Sideband Deferring.

The objective, said the Cambridge-based chip firm, is to eliminate the power drain caused by frequent polling of the Bluetooth chip by the USB subsystem.

"By working closely together, CSR and Intel have readdressed the way that Bluetooth interacts with the mainsystem and therefore how much power is consumed within the notebook PC.” said Bill Nayavich, PC market manager at CSR. 

One of Intel's techniques for saving power is to switch processors to low power sleep states when idle. An important sleep state is called C3. An integrated USB Bluetooth device can prevent the processor from entering the C3 state because it needs to be constantly polled to check whether it has any data to send to the system.

This constant polling prevents entry into C3. Bluetooth APM lowers power consumption by making sure that the Bluetooth device is only polled when it has data to pass to the system. The rest of the time the processor can enter C3.

Bluetooth Advanced Power Management is available now using firmware for the flash memory-based BlueCore4-External.

Equivalent ROM-based silicon will be sampling to lead customers in September 2008.