Delivered-To: dfarber+@xxxxxxxxxxxxxxxxxx
Date: Tue, 07 Oct 2003 05:58:14 -0700
From: Dewayne Hendricks <dewayne@xxxxxxxxxxxxx>
Startup throws cold water on hot CPUs
By Anthony Cataldo, EE Times
October 7, 2003 (2:36 a.m. EST)
URL: <http://www.eetimes.com/story/OEG20031006S0028 >
SAN MATEO, Calif. - Borrowing techniques used to make semiconductors and
pharmaceuticals, startup Cooligy Inc. says it has developed a way to cool
a CPU by etching hundreds of channels on a piece of silicon that sits on
top and circulating water through them. The water absorbs heat and
transfers it out to a radiator and fan, where it is cooled before being
pumped back to the CPU.
Cooligy (Mountain View, Calif.) had two principles in mind when it
designed the microchannels. One was to make the total area of the channels
large in order to maximize the amount of heat they can take in. If the
channels could be unfolded, their area would be about 20 times larger than
their side-to-side physical dimensions, according to the company.
Second, Cooligy wanted to keep the channels close to the surface of the
CPU, at a distance of about 1 mm, to rapidly transfer the heat. Water was
chosen as the cooling medium because of its high boiling point, although
it must stay thin and move quickly so it can be replaced by cooler fluid.
The company claims it can handle 1,000 watts per square centimeter;
today's best passive cooling systems are specified for 250 W/cm2, said
vice president of marketing Andy Keane.
Cooligy has been talking to some of the best-known CPU vendors about ways
to remove heat from their chips, Keane said, but "nobody wants to talk
about it because it speaks to speed and reliability." The only data he's
been able to disclose publicly is a seven-year-old chart showing the heat
distribution of a PA-RISC 8700 from Hewlett-Packard Co. The 3-D graph
shows heat rising like steam from a tea kettle on the corner of the die
where the chip's floating-point and integer units are congregated.
It's these hot spots, not just the overall thermal budget, that pose one
of the biggest challenges to CPU vendors and system designers. But today's
heat sinks and passive fluid heat pipes aren't up to the task, Keane said.
And it's only going to get worse as ever-finer process technologies make
the hot spots smaller and more numerous.
"It's a heat density problem arising from those parts of the chip that run
the fastest," Keane said. "At 90 and 65 nanometers, the hot spots get too
small for passive [cooling] technologies." The fastest chips can go as
high as 75 degrees C to 95 degrees C.
The Cooligy system uses an electrokinetic pump to circulate water from the
chip to the radiator. Water flows through a porous glass disk that is
negatively charged. When a positive electric field is applied, hydrogen
ions push water through the openings. It's a well-understood effect, and
is commonly used as a filter in the biological sciences, Keane said.
Founded last year by three Stanford University mechanical-engineering
professors, Cooligy said it has already developed a prototype system with
the help of companies like Intel, Apple Computer and Advanced Micro
Devices. Cooligy expects to field the first samples of its Active
Micro-Channel Cooling devices next quarter to makers of high-end systems
like workstations and 1U servers. Keane said they will be priced in the
$25 to low-$30s range.
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