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By Norman Quesnel, Senior Member of Marketing Staff
Advanced Thermal Solutions, Inc.

(This article will be featured in an upcoming issue of Qpedia Thermal e-Magazine, an online publication dedicated to the thermal management of electronics. To get the current issue or to look through the archives, visit http://www.qats.com/Qpedia-Thermal-eMagazine. To read other stories from Norman Quesnel, visit https://www.qats.com/cms/?s=norman+quesnel.)

Almost as long as personal computers have been around, users have been making modifications “under the hood” to make them run faster. A large segment of these users are overclockers, who make adjustments to increase the clock speeds (the speed at which processors execute instructions) of their CPUs and GPUs.

Many PC gamers get into overclocking (OC) to make their programs run faster. Gamecrate.com, a gamer site, defines overclocking as the practice of forcing a specific piece of hardware to operate at a speed above and beyond the default manufactured rating. [1]

To overclock a CPU is to set its clock multiplier higher so that the processor speeds up. For example, overclocking an Intel Core i7 CPU means to push its rated clock speed higher than the 2.80 GHz that it runs at “out of the box.” When performed correctly, overclocking can safely boost a CPU’s performance by 20 percent or more. This will let other processes on a computer run faster, too.

Fig. 1. An Intel Core i5-469k Processor Can Be Overclocked to Run 0.5-0.9 GHz over Its Base Frequency. Air Cooling is Provided by a Hyper D92 from Cooler Master.[2]

To serve the global overclockers market, some chip makers keep the door open to overclocking by allowing access to their multipliers. They do this with a variety of “unlocked” processors. Intel provides many unlocked versions of their processors, as denoted with a ‘k’ at the end of their model number.

For example, the Skylake Core i7-6700k and Haswell-E Core i7-5820k are made with unlocked clock multipliers. In fact, Intel targets overclockers with marketing campaigns and support services.

Fig. 2. Intel Actively Targets Overclockers with Its Unlocked Processors.[3]

Besides gaming, overclocking can improve performance for applications such as 3-D imaging or high-end video editing. For GPUs, faster speeds will achieve higher frames per second for a smoother, faster video experience. Overclocking can even save money, if a lower cost processor can be overclocked to perform like a higher end CPU.[4]

For many gamers, overclocking enhances their enjoyment by giving more control over their system and breaking the rules set by CPU manufacturers. One overclocker on Gamecrate.com said, “Primarily, I like to do it because it’s fun. On a more practical note it’s a great way to breathe some life into an old build, or to take a new build and supercharge it to the next level.”[1]

Heat Issues from Overclocking

Overclocking a processor typically means increasing voltage as well. Thus, the performance boost from overclocking usually comes with added component heat that needs to be controlled. Basically, the more voltage added to components, the more heat they are going to produce. There are many tutorials on overclocking and most of these resources stress that it’s essential to manage a component’s increased heat.[5]

Programs are available that monitor the temperature of a processor before and after overclocking it. These programs work with the DTS, digital thermal sensors that most processor manufacturers include inside their component packages. One such program is Core Temp, which can be used with both Intel and AMD cores. Some component OEMs also offer their own software to monitor temperatures in their processors.[6]

Fig. 3. The Core Temp Program Can Display Temperatures of Individual Cores in a System.[6]

Typically, an overclocker will benchmark a CPU or other component to measure how hot it runs at 100 percent. Advanced users can manually do the overclocking by changing the CPU ratio, or multiplier, for all cores to the target number. The multiplier works with the core’s BCLK frequency (usually 100) to create the final GHz number.

Tools like the freeware program Prime95 provide stability testing features, like the “Torture Test,” to see how the sped up chip performs at a higher load. These programs work with the system’s BIOS and typically use the motherboard to automatically test a range of overclocked profiles, e.g. from 4.0-4.8 GHz. From here, an overclocker may test increasing voltages, e.g. incrementally adding 0.01 – 0.1 V while monitoring chip stability.

An overclocked component’s final test is whether it remains stable over time. This ongoing stability will mainly be influenced by its excess heat. For many overclocked processors, a robust fan-cooled heat sink in place of the stock fan is essential. For others, only liquid cooling will resolve excess heat issues.

Fan Cooling

The advantage of using air coolers is no worry about leaking, which may lead to component or system damage. With the air cooled heat sinks, the bigger and faster the fan (CFM), the better, and there are a multitude of fan-sink cooling solutions that gaming PCs can accommodate.

In reality, higher performance fan-cooled sinks typically also employ liquid. It is used inside heat pipes that more efficiently convey heat from the processor into the sink’s fan cooled fin field.

Fig. 4. The Top-Rated Hyper 212 EVO CPU Air Cooler from Cooler Master Has Four Heat Pipes Transferring Heat to Aluminum Fins.[7]

Air cooled heat sinks for overclockers cost well under $50 and are available from many sources. They’re often bundled with overclock-ready processors at discounted prices.

A greater issue with air cooling can be the fan noise. A high performance fan must spin very quickly to deal with heavy system workloads. This can create an unpleasant mixture of whirs, purrs and growls. Many of the gaming desktops generate 50-80 decibels of noise at load. Though most fans are quieter, pushing out 25-80 CFM, they are louder than most standard PC processor fans.[8]

Liquid Cooling

Liquid cooling has become more common because of its enhanced thermal performance, which allows higher levels of overclocking. Prices are definitely higher than air-cooled heat sinks, but liquid systems offer enthusiasts a more intricate, quieter, and elegant thermal solution with definite eye-appeal.

From the performance standpoint, liquids (mainly water in these systems) provide better thermal conductivity than air. They can move more thermal energy from a heat source on a volume-to-volume basis.

Fig. 5. The Top-Rated Nepton 280 Liquid CPU Cooler Has a Fast Pump Flow and a Large Radiator Cooled with Dual Fans that Reach 122 CFM Airflow.[9]

A typical liquid cooling system features a water block that fits over the overclocked CPU, a large surface area, a fan-cooled heat exchanger (radiator), a pump, and a series of tubes connecting all elements. One tube carries hot fluid out from the water block, the other returns it once it is cooled by the radiator. Some liquid cooling systems can also be used on multiple processors, e.g. a CPU and a gaming chipset.

While there are more components to a liquid cooling system, there are also major advantages. For one, the water block is usually much smaller and lower-profile than an attached, high-performance air cooler. Also, the tubing set up allows the heat exchanger and pump to be installed in different locations, including outside the PC enclosure. An example is the Sub-Zero Liquid Chilled System from Digital Storm. It unlocks overclocks of Intel’s i7-980X CPU up to 4.6 GHz while idling the processor below 0°C.[10]

Fig. 6. Digital Storm’s Cryo-TEC System Places an Overclocked CPU in Direct Contact with Thermo-electric Cold Plates Dropping Core Temperatures to Below 0°C.[11]

Prices for liquid cooling systems can easily surpass $200, though newer systems can be bought for under $100.

A fan still must be attached to the radiator to help cool it, but it doesn’t have to spin as quickly as it would if it were attached to a heat sink. As a result, most liquid-cooled systems emit no more than 30 decibels.

Conclusion

Overclocking can be considered a subset of modding. This is a casual expression for modifying hardware, software or anything else to get a device to perform beyond its original intention. If you own an unlocked CPU you can get significant added performance, for free, by overclocking the processor. When modifying processor speeds, i.e. increasing them, high temperatures will occur. Higher performance cooling solutions are needed.

Fig. 7. YouTube Video of Overclocked CPU Melting Solder Before It Stops Working at 234°C.[12]

To serve the world of overclockers, a steady stream of air and liquid cooling systems are being developed. Many of them are high precision, effective, stylish and surprisingly affordable. Often they share the same technology as mass market quantity, lower performing cooling systems (basic heat sinks, heat pipes, for example), but provide much higher cooling capabilities for ever-increasing processor speeds.

References
1. Gamecrate.com, https://www.gamecrate.com/basics-overclocking/10239
2. Techreport.com, http://techreport.com/review/27543/cooler-master-hyper-d92-cpu-cooler-reviewed/3
3. Legitreviews.com, http://www.legitreviews.com/intel-devils-canyon-coming-this-month-intel-core-i7-4790k-core-i5-4690k_143234
4. Digitaltrends.com, http://www.digitaltrends.com/computing/should-you-overclock-your-pcs-processor/
5. Techradar.com, http://www.techradar.com/how-to/computing/how-to-overclock-your-cpu-1306573
6. Alcpu.com, http://www.alcpu.com/CoreTemp/
7. Coolermaster.com, http://www.coolermaster.com/cooling/cpu-air-cooler/hyper-212-evo/
8. Digitaltrends.com, http://www.digitaltrends.com/computing/heres-why-you-should-liquid-cool-your-cpu/
9. Coolermaster.com, http://www.coolermaster.com/cooling/cpu-liquid-cooler/nepton-280l/
10. Gizmodo.com, http://gizmodo.com/5696553/digital-storms-new-gaming-pcs-use-sub-zero-liquid-cooling-system-for-insane-overclocks
11. Digitalstorm.com, http://www.digitalstorm.com/cryo-tec.asp
12. Youtube.com, https://www.youtube.com/watch?v=9NEn9DHmjk0

For more information about Advanced Thermal Solutions, Inc., its products, or its thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.