Reduction of power used by transceivers in a data transmission loop

Abstract

Transceivers are selectively activated to reduce power in a network of data processing devices linked by a data transmission loop. Each of the devices is linked by a transceiver, and passes data from a previous device in the loop to a next device in the loop when not transmitting data onto the loop. For example, the data processing devices are disk drives in a storage subsystem. Delays in establishing communication after transceiver activation can be avoided by continuously powering a bit clock oscillator or bit synchronizer. In one embodiment, a loop controller in the loop sends activation and deactivation signals to addressed transceivers via an auxiliary channel. In another embodiment, when a device detects that communication is occurring between other devices for a certain period of time, the device selectively deactivates its transceiver for the certain period of time. For redundancy, the data processing devices can be connected via dual loops, and then power is further reduced by activating at most one of the two transceivers in a device at any given time. In this case, if a transceiver failure occurs, the failed transceiver is bypassed and the other transceiver for the device is activated. For example, when a loop controller detects a transceiver failure, the loop controller sends transceiver activation and deactivation signals over the auxiliary channel.