Articles: CPU

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All CPU tests we conducted in our lab always include a few mandatory aspects. Among them are performance, overclocking potential as well as power consumption and heat dissipation measurements. This set of practical data turns out more than enough to shape up very insightful and detailed opinion about the solution using its price as a starting point. However, in this case a number of important issues that could be of interest to both: enthusiasts as well as just curious users, remain left out. So, today we decided to veer away from our traditional plan and carry out a not very common CPU test session. Namely, we are going to put aside pricing and absolute performance and focus mainly on overclocking and power consumption.

There is hardly anything surprising about the increase in power consumption when the processor clock frequency increases. We have long known that these two parameters are in proportional dependence to one another. However, overclocking requires core voltage increase, then the thermal and electrical parameters will increase according to square-law. However, these two elementary rules also contains a few unknown proportion coefficients depending on processor microarchitecture, number of cores, manufacturing process used for the CPU die, etc. that is why there is no universal formula that will allow to estimate the heat dissipation and power consumption of any overclocked processor. And since we can’t seem to find a definite theoretical answer regarding the effects of overclocking on the CPU power consumption and heat dissipation, we have no other choice but to turn to practical experiments.

This test session is going to be extremely interesting and acute because overclocking has become a very popular phenomenon these days. The times, when only selected enthusiasts with extensive knowledge of computer hardware and advanced soldering skills could handle overclocking are long gone. Today most existing platforms allow CPU overclocking that can be configured with a few simplest adjustments in the mainboard BIOS Setup. As for contemporary processors, they possess significant hidden frequency potential. Even without any specific technical tricks their frequency can almost always be increased by 20-30% above the nominal, and if you are lucky, you can push it up to 50% higher.

All this results from new way the CPU manufacturers started to declare their product clock speeds. It is no news any more that they use the same manufacturing process for the fastest as well as slowest models in the lineup, so that the junior models can eventually work at the top model frequencies. Overclockers have been taking advantage of this peculiarity of the production process for over two decades already. However, these days there is a new aspect to it. The top processor frequencies used to be set according to the frequency potential of the semiconductor dies. Now that the CPUs have become much more complex, which resulted into higher thermal and electrical readings, they also take into account such parameters as power consumption and heat dissipation when they determine the nominal CPU clocks. In other words, it is often not the potential of the semiconductor dies used for the processor in question, but their heat dissipation that act as a limiting factor for their nominal clocks.

For example, contemporary desktop processors have several typical limitations for average heat dissipation under heavy load: 130 W or 95 W for performance models, 73 W or 65 W for mainstream and budget models. As a result, although many mass production semiconductor processor dies can easily work at 4 GHz frequency, the actual processor built on them cannot boast having a nominal frequency like that, because in this case their heat dissipation will be beyond the acceptable maximum. The TDP restrictions are absolutely justified: first of all, they are determined by the efficiency of existing cooling systems priced acceptably for each given price range; and second, by the constructive peculiarities of processor voltage regulator layout on the boards.

This is where two possible conclusions come to mind. First, overclocking as a way to boost the performance is one of the effective and pretty affordable options for anyone. Contemporary processors have substantial hidden frequency potential, which can be put to good use without much effort. Most contemporary mainboards provide the users with all necessary tools for that matter. Second, if you decided to resort to CPU overclocking, you have to be prepared to deal with its increased heat dissipation and power consumption even when these values go beyond the calculated TDP thresholds. Processor cooling system should be efficient enough, and its onboard voltage regulator circuitry should be able to handle currents exceeding the nominal values.

In our today’s article we are going to discuss how processor power consumption (and heat dissipation that is directly connected to it) changes during overclocking. Namely, we do not need any tests to show us that platforms power consumption increases in this case. But it is definitely very interesting to see how greatly the electrical and thermal parameters of the processors in question change when their clock speeds increase. How big of a reserve should overclocker mainboards and cooling solutions have? How seriously will the system’s energy-efficiency suffer during overclocking? What power supplies would be sufficient for enthusiasts’ needs? These are a few questions our today’s article intends to answer for you.

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