May 9, 2007

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IBM developes high thermal conductivity interface technology

April 9, 2007

This could be a good solution for cool and quiet processor and chipset cooling:

Using a technique based on the human circulatory system, IBM researchers today presented an approach for improving the cooling of computer chips.

Delivered at the BroadGroup Power and Cooling Summit in London, IBM researchers discussed the technique, called “high thermal conductivity interface technology,” that they claim allows a twofold improvement in heat removal over current methods.

The technique is one of several being explored by scientists from the IBM Zurich Research Laboratory to address the problem of excessive heat brought on as performance continues to progress according to Moore’s Law.

“Electronic products are capable of amazing things, largely because of the more powerful chips at their heart,” said Bruno Michel, manager of the Advanced Thermal Packaging research group at IBM’s Zurich lab, in a statement this morning. “We want to help electronics makers keep the innovations coming. Our chip-cooling technology is just one tool at our disposal to help them do that.”

The approach used by IBM addresses the connection point between the hot chip and the various cooling components used to draw the heat away, including heat sinks. Currently, special particle-filled viscous pastes are typically applied to this interface to guarantee that chips can expand and contract with the thermal cycling. This paste is kept as thin as possible in order to transport heat from chip to the cooling components efficiently. However, IBM warned, squeezing these pastes too thin between the cooling components and chip would damage or even crack the chip if the conventional technologies are used.

To alter that, IBM researchers developed a chip cap with a network of tree-like branched channels on its surface. The pattern is designed such that when pressure is applied, the paste spreads much more evenly and the pressure remains uniform across the chip, allowing the right uniformity to be obtained with nearly two-times less pressure, and a 10-times better heat transport through the interface, according to IBM. IBM credited the design’s idea to biology, where systems of hierarchical channels can be found manifold in nature or the human circulatory system.

Looking Ahead to Water Cooling

The prototype demonstrated at today’s summit is part of a large effort within IBM’s Research and Development organizations to improve cooling performance of next and future generations of computer systems. Noted IBM, the cooling bottleneck results from the demand for more powerful computer chips, a severe constraint on overall chip performance, and added that today’s high-performance chips already generate a power density of 100 watts per square centimeter. Tomorrow’s chips may attain even higher power densities, IBM said, projecting surface temperatures close to that of the sun when not cooled (approx. 6000 °C).

Current cooling technologies, mainly based on forced air convection, or fans, blowing across heat sinks with densely spaced fins, have essentially reached their limits with the current generation of electronic products, according to IBM, which also pointed out that the energy needed to cool computer systems is rapidly approaching the power used for calculations, thus almost doubling the overall power budget.

“Cooling is a holistic challenge from the individual transistor to the datacenter. Powerful techniques, brought as close as possible to the chip right where the cooling is needed, will be crucial for tackling the power and cooling issues,” Michel said.

Beyond air-cooling systems, IBM’s Zurich researchers are taking their branched channel design and are developing an approach for water-cooling. Called direct jet impingement, it squirts water onto the back of the chip and sucks it off again in a closed system using an array of up to 50,000 tiny nozzles and a complicated tree-like branched return architecture, the company described.

Lab results of the water technique have demonstrated cooling power densities of up to 370 watts per square centimeter, more than six-times beyond the current limits of air-cooling techniques on less energy for pumping than other cooling systems do, IBM said.

Hello to the world of noiseless Silent PCs!

December 31, 2006

A Silent PC is called a PC , whose noise level was reduced by special measures.

Current computers with high end hardware produce high temperatures. While the first PCs onlyhad an electrical power consumtion of a few Watts and no special cooling of components was needed, the hunt of the manufacturers and consumers for higher performance at lowest prices led to an enormous power consumtion and heat emission of PCs in the meantime. The fact that same performance is possible with substantially smaller energy consumtion also shows e.g. the notebook technology.

For the dissipation of the amounts of heat usually small exhausting fans are used, which cause substantial noise. This problem can be reduced or eliminated by modification and correct choice of the components purchased. Passive cooling concepts, which get along completely without fans, promise complete avoidance of exhausting noise.


Power Supply

The fans of standard power supplies are mostly very loud, since they run in each operating phase with the highest speed. Here the noise level can be very strongly reduced by a temperature-controlled cooling fans. In addition there are silent power supplies to be mentioned, which are equipped mostly with one 120 mm or 140 mm fan which is able to push larger air volumes at lower speeds more. However these power supplies are mostly clearly more expensive. If the pc already has a noisy power pack, a change of the power pack exhausting fan to a quieter (running in ball bearings) model will make sense. The change should be made exclusively by a specialized company, since mortal danger exists. A more expansive solution is to replace the power supply to a passively cooled model.

The Processor Cooling

At first here should be noticed that a processor cooler with a very good heat dissipation (e.g. with copper core) should be used. With the CPU purchased Standard Processor coolers are in most cases not adjustable, and will run in the normal operation with constant 12 V. Various manufacturers offer coolers with adjustable fans, which make an operation possible with 12 V and with 7 V. The noise level sinks with the jump from 12 V to 7 V over approx.. 30% while offering approximately the same cooling performance. Also a passive cooling or water cooling is possible, however at a clearly higher price.

System Cooling

Here should be already paid attention at the purchase to a good and quiet cooling, because with a modification immediately any warranty gets lost. Here something similar applies as for the processor cooling that a loud cooling not automatically means also a good cooling performance. Meanwhile some very good and quiet cooling fans are available but the best and a noiseless system would only be possible with passive cooling.

Harddisk damping

If one has undertaken the measures mentioned above, then one will notice that the non removable disks transfer their vibrations to the housing. The non removable disk manufacturer Seagate indicates the fact that approximately 70% of the sound produced by a non removable disk as impact sound is delivered to the case. For this reason an uncoupling is usually an amazingly effective way to get a non removable disk more quietly.

But there are finished bays and mounting plates, in which by rubbers the non removable disks are separated from the housing. Some solutions offer also additional cooling functions for the Harddisk Drive. The uncoupling is quite effective, when the non removable disks do not have a direct contact to the housing and and pass on their oscillation energy.

A quite favorable solution are conventional rubbers, with which an uncoupling for under 50 cent per non removable disk is possible.

Such self-’s building solutions can be high-grade dangerous however, if the used elastomer does not withstand the endurance stresses by heat, stretch, electromagnetic fields and ozone. Straight conventional household rubbers, as rubber seals, O-ring seals from the sanitary area, or elastic strips from the clothing industry are absolutely unsuitable.

A rise in temperature of the non removable disk by a flexible suspension actually is not to be expected usually. The non removable disk in a flexible suspension can deliver no more warmth to the (metallic) disk cage, but this heat dissipation hardly plays a role in practice. Positively however the suspension affects the direct air cooling, since the non removable disk can be flowed around by all sides.

Northbridge Cooling

Main board manufacturers again and again equip the Northbridge with an active radiator. Partially in order particularly to address Overclocker, in addition, due to the high calorific loss achievement of current chips. Due to the mostly small measured place on the motherboard, here frequently very fast running 40 mm fans are used. The exchange of these coolers usually cause the immediate loss of the warranty.

Completely Silent PCs

Some companies already offer complete PCs that were designed after acoustic objectives.

Totally noiseless and passive cooled computers are available at zalman or sizo.

Noise Measuring

In the computer range two different standarts are common for the classification of the noise emission by the equipment: The decibel scale, and the Sone scale.

The decibels, usually in the ‘ A’-weighted form (dBA), is a logarithmic scale. This means above all that the scale is not linear. Therefore a direct or intuitive comparison of two different (A) measured values is hardly possible. In addition it comes that the railway (A) scale, despite a weighting, which is taken to the human aural acuity only something over the soundness (more exact: , however nothing states the sound pressure level) of a noise over its subjectively felt as annoying.

Exactly this, much ‘ human ‘ criterion is however crucial with relatively quiet interferences. As example (subjective) the comparison between the summ of a mosquito and murmuring of a river is mentioned: Although the latter with a far higher -(A)-worth -measured, everyone will classify the summ of a mosquito as substantially more disturbing.

Therefore the decibel scale is only very conditionally suitable to make statements about the noise emission (or their absence) with computers.

Measured values are more meaningful in the sone scale, which also evaluates other factors, that play a role for the human auditory sensation. With Sone actually applies:

double value = twice as loud (and annoyingly)
To the selection of components for silent PCs, the values of the following table can apply as an orientation, whereby it is to be made sure that only such measured values are comparable, which were determined under same conditions. The weightiest factor of influence is the microphone distance to the acoustic source.

Valuation Range normal PC Range silent PC
very well 0-0.5 Sone 0-0.5 Sone
well 0.5-1.5 Sone 0.5-1.0 Sone
means 1.5-2.5 Sone 1.0-1.5 Sone
badly 2.5-4.0 Sone 1.5-2.0 Sone
very bad starting from 4,0 Sone starting from 2,0 Sone


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