Electronic Design

Emerging Ethernet Enhancements Engender Energy Efficiency

Back in 2002, the U.S. Department of Energy said the nation’s enterprise IT equipment ate 97 terawatt hours per year—and that didn’t even include the power required to cool all that gear, which probably would boost that figure by 50% or more. Of course, even more power is being burned today, and companies like Vitesse Semiconductor are responding with innovative software solutions.

Most equipment includes Ethernet connectivity nowadays, providing lots of potential for energy savings. For example, Vitesse’s ActiPHY saves energy by automatically turning off ports on Ethernet switches when they aren’t being used (see the figure). A built-in random pulse link sleep timer wakes the chip up if activity occurs. This can save a lot of power, especially in larger multiport switches.

Also, the company’s PerfectReach smart cable technology adjusts the drive power level to the cable to match the link length. Most Ethernet chips implement a driver with the needed power level to the cable to meet the maximum Ethernet standard that ensures a solid signal at the limit, usually 100 m. Many connections are much shorter than 100 m, meaning lots of wasted power. PerfectReach adopts algorithms that can examine the settings of the output (equalization, etc.) to roughly determine cable length and reduce the power level accordingly. Energy savings up to 10% are possible.

Vitesse is also part of the IEEE’s new effort to help produce a more efficient Ethernet. A new task force designated 802.3az is seeking methods that can greatly reduce Ethernet power consumption. One goal is to reduce power when idling in link speeds using 100BaseTX and 1000BaseT. Other approaches to be examined include scaling power to data bandwidth usage and using sleep/standby modes when there is little activity. While a standard isn’t expected for a year or so, you can pick up some good power savings with the Vitesse efforts.

Vitesse’s energy efficiency solutions can be used with any of its Ethernet chips, including the low-end SimpliPHY, SparX, and G-RoX devices for one to eight ports, the SimpliPHY and SparX chips for 16 to 24 ports, and the high-end SimpliPHY and SparX devices for applications with 24, 48, or more ports. Physical-layer (PHY) application programming interfaces (APIs) for these chips are available.

Vitesse Semiconductor Corp.


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