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Overclocking at DreamHack Summer 2005 - Day 2 - Dry ice

For friday we had ordered 17 kilograms of dry ice. Many people who visited our booth had the opportunity to encounter this "ice". Dry ice is carbon dioxide in solid form that has the property of transferring to gas form at -78 degrees celsius. If you put the ice itself in a liquid, the temperature of the liquid will drop to below -70 degrees celsius. That's the property you take advantage of when you use dry ice for processor cooling.

A copper container was mounted on the processor and filled with dry ice and ethanol. The reason we use ethanol is so that it doesn't freeze at these low temperatures but maintain the heat conductivity between the fluid and the container. When the temperature had dropped below 0 degrees, the system was started and we booted up Windows, awaiting the temperature in the copper container to drop. At roughly -60 degrees we began testing how everything performed. When the whole system was acting very unstabile and began to reboot at 4900 MHz, we suspected that the pressure was too bad between the copper container and the processor. The system was shut down and the screws were tightened. When we started it again, the motherboard refused to POST. Fearing that we had just killed a motherboard, the container was taken off and the compressor cooling was mounted. With great relief, we saw the system POSTing again. Without knowing what had caused the error, we suspect that the capacitors were too cold and lost their electrical properties. After asserting that the processor still was in great shape, we decided to give the dry ice one more chance and mounted the copper container once again.

Now that we knew that we couldn't run in any longer periods because of the coolness, we started the system and immediately began fighting for reaching the maximum frequency. This time the system acted a lot better than before and with a vcore of 1.750V, we touched our previous record of 5066 MHz. 5100 MHz was also working fine. 5150 MHz aswell. But at 5200 MHz we hit a wall. Fortunately, the motherboard went through the POST process after the reboot and we could increase the voltage even more. 1.760V turned out to be enough for 5200 MHz so we went to the next step, 5253 MHz. Reboot again. Once again we could just cross our fingers for the motherboard to be able to handle a start, which it also did. The voltage was increased to 1.770V. Judging from the great voltage increase, we realized that we were very close to the limit of the processor. 5253 MHz was barely passed. We didn't even know if the screenshot had been saved or not. Immediately after the buttons for screenshot and verification had been pressed, the system restarted and the bug we earlier had encountered was once again appearing. The only choice we had was to unmount the container and see if the hardware was still alive with air cooling. It turned out that we had saved the screenshot and verification file before the computer was restarted.

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