Intel touts direct DC power supplies for power savings

Posted by Humphrey Cheung

San Francisco (CA) - It should come as no surprise that server computers use a lot of electricity, but Intel's CTO Justin Rattner says much of that power is wasted and of course he has a solution. Speaking at the Intel Developer's Forum, Rattner said direct current power supply units (PSUs), the ones that don't need AC power, could save an extra 14% over existing high-efficiency PSUs. Rattner even demonstrated a prototype DC PSU and proclaimed that it had an efficiency of greater than 90%.


slide show: Chief technology officer Justin Rattner talks about Direct DC PSUs ...

Rattner explained that traditional power supplies are only 55 to 70% efficient and that up to two-thirds of the power going into a system goes up as waste heat. Intel has been working on more efficient single voltage rail PSUs that are 90% efficient, but Rattner explains that isn't enough.

Google distinguished engineer Luiz Barroso conveniently showed up to explain just how important power costs are to server farms, something Google obviously knows a thing or two about. Barroso said the total power costs for a server eventually outstrips the hardware cost at the three to five year point. Keeping electricity costs down is the main reason large companies like Microsoft and Google are building data centers in the Pacific Northwest where cheap hydroelectric power abounds.

Power is also wasted when electricity is constantly being converted from direct current to alternation current and vice-versa. This often happens in data centers where the current coming from the main power lines hit converters, uninterruptible power supplies and eventually the computer PSU itself.

Rattner brought out fellow Intel employee Tom Aldridge to show off a new PSU that could use DC power directly. Aldridge first held up the older single voltage rail power supply and claimed the new unit would be even more efficient. At the urging of Rattner, Aldridge dumped the PSU into a trashcan, appropriately labeled the "Dustbin of Obsolescence". Rattner peeked into the dustbin and couldn't resist a verbal jab at AMD: "It looks like there is an Opteron in here," said Rattner.

Rattner and Aldridge pitted two servers using the older and newer PSUs against each other, under full load. The older PSU-powered server guzzled 3837 watts, while the newer server used 3333 watts of power, a 15% reduction in power. Rattner said companies could either bank the monetary savings or build more servers in a data center for the same energy cost.

Intel hasn't said if it plans to move direct DC power supplies down to the desktop level.

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