An interesting article on how stay Cool ;-)
ebnews.com
OEMs confronting thermal issues in gigahertz-plus PCs
By Mark Hachman
Electronic Buyers' News
(04/07/00, 08:25:52 PM EST)
As microprocessors break the 1-GHz barrier, PC OEMs and component designers are facing the growing challenge of how to cool their components without resorting to new, expensive alternatives.
Already a watchword in the portable-electronics industry, thermal management as it is applied to notebook PCs often requires custom designs that minimize heat through the use of exotic materials and cooling solutions. The hurdle now is to accomplish the same task in the desktop segment, but through the use of conventional, inexpensive techniques that are easy to mass produce.
What's more, as PC components grow increasingly sophisticated and throw off greater levels of unwanted heat, the problem becomes more than just a thermal issue.
According to fan manufacturers, more robust cooling methods are bumping into vendor-imposed acoustical limits, which are leading them to develop or license new sound-dampening technologies -- at an added cost. And ever-hotter microprocessors may force OEMs to qualify new, larger fans, which in turn could cause them to redesign their boxes in the process.
Earlier this week, Intel Corp. and Microsoft Corp. released the first draft version of their PC2001 specifications, which require less than 37 dB of acoustical noise -- measured according to ISO standards -- for PCs shipping in the second half of 2001. Should a PC OEM fail to meet this standard, it could lose the Windows Hardware Quality Laboratory certification that Microsoft requires before it authorizes use of its Windows operating system.
To help solve the problem, the Intel Architecture Laboratories last month released a set of guidelines detailing a series of component-level initiatives for cooling PCs running at 1 GHz and faster, and suggesting the use of larger fans.
At the heart of the thermal issue is Moore's Law, which states that the number of transistors on a given die area will double every 18 months. As the number of transistors increases, however, so does the resulting waste heat. Designers have traditionally turned to process shrinks to reduce the operating voltage and thermal energy. But microprocessor makers have also tended to use the shrinks to ratchet up clock speed, increasing heat yet again.
Intel recommends that the ambient temperature above a microprocessor be less than or equal to 40øC. According to the company's high-performance ATX-desktop guidelines, PC chassis that exceed the limit ?are unlikely to support future cost-effective package-level solutions,? a reference to Intel's return to ?socketed? processors that use a smaller package.
As they've evolved, the power consumption of Intel processors has climbed from 4 to 5 W in 486 devices to a high of 39 W in the 300-MHz Pentium II, according to Jeff Austin, technical marketing manager at Intel in Hillsboro, Ore. ?And I think in the next generation we'll go a little bit higher,? he said.
The fastest 1-GHz Coppermine draws 33 W, a pittance compared with the 1-GHz Athlon from Advanced Micro Devices Inc., which almost doubles heat output to 65 W. Compaq Computer Corp.'s 600-MHz Alpha 21264, a chip primarily used in more expensive workstations, produces an amazing 104 W of waste heat, according to Kim Noer, a doctoral student working at the Northwood Corp. in Denmark, who has assembled a CPU power-dissipation database culled from chip industry data sheets.
The CPU is not the only culprit, however. Power consumption is on the rise in chipsets, DRAM modules (especially Direct Rambus DRAM), and AGP graphics cards, the latter of which now ship with on-board fans of their own.
To cool the system, one 80- or 90-mm fan is typically built into the PC's power supply, which exhausts hot air through holes bezeled into the chassis. A second 80-mm fan may also be built into the back of the case. A third option is to clamp an additional 60-mm fan onto the microprocessor die itself, which generally has been left bare in recent chip-level package redesigns to assist cooling. Older plastic chip packages can trap heat, Intel's Austin said.
With all of those fans running at full speed, a PC can quickly push the acoustic noise beyond PC2001-certified limits.
Given the noise considerations, acoustics have become part of an OEM's ?wish list,? said Fernando Palarca, sales manager at NMB Technologies Inc., Chatsworth, Calif., which has been looking at different ways to reduce acoustical system noise. The problem, he said, is that a 90-mm fan typically costs about $3 to $4 in OEM quantities. Tacking on a third-party IP license adds about 30 to 50 cents to that cost.
From a CPU standpoint, Intel will probably apply techniques used in battery-operated processors for mobile applications, according to Austin, helping to minimize the cost to an OEM. ?There are a lot of mobile-design techniques, and we can leverage off of our ingenuity there,? he said. ?Also, there's a lot of logic in there that's mutually exclusive [and can be turned off], ... but it needs to be a very manufacturable solution.?
Intel Architecture Labs, the company's research arm, has also spent considerable effort researching the problem, noted Bill Colson, marketing manager for scalable platforms. ?We can solve this problem with commodity parts today, but we're working on different ways of getting there,? he said.
Instead of using multiple fans to suck air out of the system from holes cut into the case, Intel's favored method involves drawing in cool, fresh air from outside. Because the processor, chipset, Direct Rambus memory, and AGP graphics card are often found near each other on a motherboard, a single 120-mm ?ceiling fan? can be used to blow cool air directly on what Intel terms the ?core area,? Colson said.
This means that those components will have to be oriented in a specific layout to maximize cooling, so the current ATX motherboard specification is being revised to address that, Colson said.
Intel is also working to develop high-aspect-ratio heat sinks, metal plates that attach to the outside of a chip with built-in ?heat pipes? that transfer heat via a liquid-filled channel away from the CPU.
Additionally, the company hopes a forthcoming New Power Supply Architecture guideline will help eliminate switching in PC power supplies, allowing system designers to do away with the power-supply fan entirely in favor of a single-fan ducting method.
Intel and OEMs like Dell Computer Corp., Round Rock, Texas, have also realized that buying and installing temperature sensors around the PC case and integrating them with other system components can allow a fan to be slowed down when the PC is being lightly used, said Kevin Kettler, Dell's director of architecture and technology. ?The key thing is that you do [PC] designs as a whole-box profile,? he said.
While Dell has climbed to the top spot in U.S. PC shipments by streamlining manufacturing costs and delivery times, thermal management is an area the company takes seriously. ?Decisions like reducing two fans to one are things we consider to be value propositions,? Kettler said. ?That's why we do it in-house, because we think it's a differentiating feature.?
Even at the component level, intellectual-property houses are springing up to combat the problem of noise. Lemont Aircraft Corp., an IP house in Ansonia, Conn., claims to have developed a fan-manufacturing technique to cut acoustical noise 7 to 12 dB by eliminating the vortex a fan causes when it rotates, according to Andrew Lemont, corporate vice president.
The company has licensed its technology to NMB Technologies and Panasonic Industrial Co.; NMB's DC3610KL ducted fan began shipping in January using the new technique.
?I've gotten a little frustrated over the years,? Lemont said. ?I always knew acoustics was going to be an issue.? |
