Water-Cooled Personal Computers: a Case Study
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Colder Computing Goes Consumer Water-Cooled Personal Computers: A Case Study January 2003 DRAFT David Hesprich Principal Engineer ManTech Security Technologies Corporation 6400 Goldsboro Rd, Suite 200 Bethesda, MD 20817 Table of Contents Introduction ___________________________________________________________ 1 The Cooling Problem as Driven by the Enthusiast Market ______________________ 2 Passive and “Silent” Cooling __________________________________________________ 3 “Extreme” Cooling __________________________________________________________ 3 Liquid Cooling _____________________________________________________________ 4 Water-Cooling’s Current State of the Art ____________________________________ 6 Enthusiast Cooling Goes Industrial ____________________________________________ 6 Consumer Level Water-Cooling _______________________________________________ 6 Casing the Case Study ___________________________________________________ 9 Installation________________________________________________________________ 11 Installing the Coolers______________________________________________________________ 11 Filling _________________________________________________________________________ 13 Final Assembly __________________________________________________________________ 13 Performance ______________________________________________________________ 13 Conclusion ___________________________________________________________ 15 Appendix I - Aesthetics _________________________________________________ 16 Front Bezel _______________________________________________________________ 16 Case Interior ______________________________________________________________ 18 System Information Display _________________________________________________ 21 Appendix II - Overclocking ______________________________________________ 22 Advantages of Overclocking _________________________________________________ 22 Risks of Overclocking_______________________________________________________ 22 Reliability ______________________________________________________________________ 22 Warranty _______________________________________________________________________ 22 Catastrophic Failure_______________________________________________________________ 23 Making the Decision to Overclock_____________________________________________ 23 Determining Needs and Wants ______________________________________________________ 23 Economy vs. Performance__________________________________________________________ 24 When to Hold ‘Em, When to Run _____________________________________________ 24 References and Works Cited _____________________________________________ 26 Water-Cooled PCs ii ManTech Security Technologies Corp. Introduction In the beginning, there was passive cooling, and it was good… enough. The original IBM PC (a named later used to refer to all personal computers), Model 5150, was released in September 19811. It used an Intel 8088 processor, running at 4.77 MHz. Cooling for the processor consisted only of what air the single power supply fan drew across the face of the processors’ DIP package. Modern processors, at considerably higher clock speeds and feature density, generate far more heat than the venerable IBM PC. The typical heat dissipation of the Pentium 4 3.2 GHz processor equals 82W2. Cooling solutions now require a great deal more precision and efficacy to reliably operate a specific processor. Likewise, the rapid heat escalation in video cards could some day overtake processors in heat output. Other components such as high-RPM hard drives have also followed this tendency toward higher heat outputs with each consecutive generation. Heatsinks and heatsink/fan combinations of varying size, shape, and materials are now expected to perch on top of the processor and in many cases the RAM and support chipsets as well. Heat-producing devices in a typical computer are cooled by air using these heatsinks. Heat generated from the components is transferred into a metal heat sink, where a fan blows air across its wider surface area. While altering a heat sink’s size and composition can improve the effectiveness, it is still limited because air absorbs and transfers heat very slowly. To counteract the low thermal conductivity of air, more air can be moved across the heatsink. However, higher fan speeds equate with high noise. As systems continued to produce more heat, required heat sinks get larger and louder. Of liquids, water (after mercury) conducts heat the fastest. Its thermal conductivity is about 30 times greater than that of air. Water is also capable of holding four times the heat of air. These physical characteristics give water-cooling a distinct advantage, although not just in thermal performance. Water-Cooled PCs 1 ManTech Security Technologies Corp. The Cooling Problem as Driven by the Enthusiast Market The ABC sitcom Home Improvement starring Tim Allen popularized the phrase “more power!” However, long before the TV show, the phrase still existed as one of the primary motivators of the enthusiast. The hardcore enthusiast seeks to get the most power for the smallest investment, will do whatever it takes to get it. It was not long before computing enthusiasts learned of the possibilities inherent in conservative engineering designs for experimentation. The practice of overclocking began to gather a small but energetic following. overclock /oh'vr-klok'/ vt. To operate a CPU or other digital logic device at a rate higher than it was designed for, under the assumption that the manufacturer put some slop into the specification to account for manufacturing tolerances. Overclocking something can result in intermittent crashes, and can even burn things out, since power dissipation is directly proportional to clock frequency. People who make a hobby of this are sometimes called "overclockers"; they are thrilled that they can run their 450MHz CPU at 500MHz, even though they can only tell the difference by running a benchmark program. - The Jargon File, version 4.2.2, 20 August 2000, available from http://info.astrian.net/jargon/ Higher clock speeds means more generated heat however, and heat has never been healthy for solid state devices. A need for more powerful and exotic cooling methods was generated to manage the feverish temperatures of overclocked processors. However, exotic cooling has not been driven solely by managing heat. In a similar vein as overclocking, the concept of quiet or silent computing. The goal of silent computing, while not mutually exclusive to that of overclocking, is different – to reduce or completely eliminate the generated noise of an operating computer. Considering that Delta, a popular fan manufacturer for overclockers, manufactures fans that rate at some 52dB, the sound of a running PC may range from a soft hum to the shrill whine of a vacuum cleaner. Table 1 - Noise Reference Table3 SPL (DB) TYPICAL ENVIRONMENT AVERAGE DESCRIPTION (SUBJECTIVE) 140 30 meters from military aircraft at take off Threshold of pain 120 Boiler shop (maximum levels); Almost intolerable Ships engine room (full speed) 100 Automatic lathe shop; Very noisy Platform of underground station (maximum levels); Printing press room 80 Curbside of busy street; Quite noisy Office with tabulating machines 60 Restaurant, Department Store; Noisiest Gamer PC35-45 Noisy 50 Conversational speech at 1 meter; Noisy workstation Clearly audible 35-45 Quiet office or library; Typical PC Subdued 25-30 Bedroom at night; Quiet PC Quiet 20 Quiet whisper; Very quiet PC; Background in TV and Very quiet recording studios 10 Super quiet PC Barely audible 0 ‘Normal’ threshold of hearing Not audible The introduction of PCs into the living room, as part of Digital Video Recorder (DVR) devices, and home theater applications (such as Microsoft’s entry in the market, Windows XP Media Center Edition4), there is Water-Cooled PCs 2 ManTech Security Technologies Corp. a clear reasoning behind the demand for silence. Users are looking for products that offer less or no impact on their listening experience. Passive and “Silent” Cooling Zalman Tech Co., Ltd.5 is probably one of the best-known manufacturers for enthusiast and commercial cooling products in the silent computing arena. Their products include somewhat nontraditional heatsink designs, as well as designs that use heat pipes. Figure 1- Zalman ZM6548BC-Gold "Flower" Figure 2 - Zalman ZM80C-HP Heatsink Heatsink “Extreme” Cooling Other forms of cooling include “extreme” cooling, which utilize below-ambient-temperature techniques: phase-change and Peltier. Phase-change cooling, such as that offered by the asetek6 VapoChill CPU Cooler works in exactly the same way as a household refrigerator or air conditioning unit, except here the evaporator, called a copper head, lies directly on the processor. A system such as the VapoChill can remove up to 160W of heat from the system, allowing temperatures well below freezing. Figure 3 – asetek VapoChill CPU Cooler Water-Cooled PCs 3 ManTech Security Technologies Corp. Peltier coolers, also known as thermoelectric (TE) modules, are small solid-state devices that function as heat pumps. It moves heat from one side of the device to the other. This means that a Peltier element has a hot side and a cool side. Peltier elements use electricity to perform this task, and quite a lot of it, and also generate a good portion of waste heat in the process. The temperature difference between the hot and the cold side of a Peltier element can be about 70 degrees, with some high performance Peltiers reaching up to 120