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Card cools PCs, workstations
By Rick DeMeis, Senior Technical Editor -- Design News, December 2, 2002
Newton, MA — CPUs for PCs and workstations are hot—and getting hotter. As Tomm Aldridge, director of enterprise architecture at Intel Labs, told an Internet newsletter, "We don't have to look very far into the future to see where just putting a heat sink on a processor and blowing air over it is not going to work anymore."
Well, you won't have to blow your cool, or CPU, thanks to inventor Ronen Meir, founder, president, and CEO of Active Cool (Ashkelon, Israel). He recently visited Design News to demonstrate the company's just announced thermoelectric-based PC and workstation cooling product. Echoing Aldridge, Meir says that next year CPU power should hit a level of around 85W, roughly the limit of what a fan/heat sink can handle. But Active Cool's AC4G, a patent-pending thermoelectric heat pump and control card, can readily handle such loads as well as monitoring and controlling processor temperatures. An added plus is being able to cut computer noise in the process.
Other active cooling techniques such as liquid-loops or vapor-phase refrigeration are available to handle these higher heat loads, but they tend to be more complex, more costly, or geared more for custom applications, according to Meir. The CPU could also be "thermal throttled" (selectively shutting down features or slowing clocks in certain functions) but that could cut performance just when or where it may be needed. The thermoelectric method, as demonstrated to Design News, is generic, based on a card that plugs into a slot in any PC and a cooler/heat sink/fan unit that clips onto the CPU.
"The key is power—how you power the thermoelectric cooler within the form factor," says Meir. To fit on the card, Active Cool uses a planar transformer with high frequency switching (switched mode power supply) that he says is 90% efficient compared to 70-75% for other transformers. A separate wall plug power cord runs to the card so that computer power is not tapped for the cooling functions, which are 4W in a sleep mode, 15W in typical continuous operation, and 68W for a maximum heat load situation.
The controller monitors the temperature of the air inside the computer and the cold plate on the CPU. The unit also processes this information to avoid having the plate too cold, which could result in condensation. CPU processing load is also thrown into the mix of the proprietary processor algorithms. The fan can run at three settings, and usually runs slower than conventional heat sink fans, cutting noise between 5 and 10 dB, depending on the mode of operation, according to Meir. The processor can drive the cooler (sandwiched between the cold plate mounted on the CPU and the heat sink with the fan on top) to respond within one second and thus fan speed may not even have to increase to handle some peak heat loads. The controller also governs fans that vent and draw air into the PC case. "Chips are expensive and you have to give enough margin for the chips to work. You have to react quickly and you can't just do it with a heat sink passively" or with a fan, he notes.
For more information on cooling cards from Active Cool, enter 536 at www.designnews.com/info.
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