Water-cooled notebooks could pave the way for high-power handheld PCs

Hitachi's three prototypes of water-cooling systems for notebook computers were unveiled in one of the quieter announcements at...

Hitachi's three prototypes of water-cooling systems for notebook computers were unveiled in one of the quieter announcements at Intel's Developer Forum, writes Eric Doyle.

In a flashback to the days of water-cooled mainframes, Hitachi is proposing to replace the fans that cool a notebook's computer chips with a circulatory system of tubes that would carry water over the microprocessors to dissipate heat. This would enable the notebook to run more quietly and possibly more efficiently.

The Silent Water Cooling System (Swacs) has been developed by Hitachi Systems' Platform Division. It will initially be used in Pentium 4-M-based notebooks when the first system ships in the autumn. The company then plans to deliver versions for desktop PCs and servers, but there is also a potential market for mobile devices.

As with all processors, as power increases so does the amount of heat produced. This creates a problem for handheld devices, which are too small to incorporate a fan. Intel has addressed the issue with its Strongarm processors, but Swacs could offer a solution that would allow more powerful processors to be manufactured from current chip technologies without heat dissipation becoming an issue.

The main advantage with Swacs is that the heat exchange can be spread more widely, and therefore more efficiently, across the body of the device. The alternative is to use heatsinks thermally coupled with the chips' fan to draw the heat away.

For the Swacs notebook implementation, the liquid - which is currently water but could in future be some other, more efficient heat-exchanging fluid - will be circulated through flexible tubes into the lid of the PC, behind the LCD display. The tubes will then be coiled across the lid's surface, exposing a large area of fluid to the room-temperature air to allow maximum cooling to take place.

Hitachi said the small pump required to circulate the fluid will produce far less noise than a fan.

Another advantage of Swacs is that one cooling system can be used throughout the device for hot-spot processors and components. In effect, this creates a miniaturised equivalent of the massive mainframe cooling plants of the 1970s and 1980s.

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