Power Consumption in Overclocked Mode
The power consumption tests performed on overclocked processors promise t be considerably less predictable. Although according to the conclusions we drew after our special investigation, we can assume that old rules will still work for both our today’s processors - Core i7-2600K and Core i7-990X Extreme Edition. These rules are the following: if the processor clock frequency increases at the constant voltage, the power consumption doesn’t increase too much; however, if the Vcore increases, then this parameter goes up, too.
Nevertheless, our practical experiments show that almost any overclocking doesn’t affect the power consumption in idle mode. This can be explained easily. C1E and Enhanced Intel SpeedStep power-saving technologies continue working as usual in overclocked systems. It is especially true in our case, when all overclocking is done by simply adjusting the processor clock frequency multipliers, so that they go back to the same power-saving mode as they would without any overclocking, when the system is idling. And even if we overclocked by raising the processor Vcore, it doesn’t change anything: the core voltage also drops to its original level in idle mode.
The only sad exception to this rule is Phenom II X6, which Cool’n’Quiet technology gets partially disabled during overclocking by multiplier for some reason.
High processor load easily destroys the idyllic picture we have just seen on the graph above. Here overclocked and non-overclocked processors demonstrate drastically different results. However, the obtained results still comply with the rule described above: only if you raise the Vcore during overclocking, the power consumption increases significantly. Namely, Core i7-990X Extreme Edition working at 4.26 GHz frequency and at default voltage consumes only 22 W more power than at its standard clock of 3.46 GHz. As for Core i7-2600K overclocked to 4.4 GHz without increasing its Vcore, its power consumption is 28 W higher than in the nominal mode. Any further overclocking of both processors (by additional 300-400 MHz) that requires higher Vcore setting, causes about 50 W increase in power consumption.
Overall, outstanding power-efficiency of the Sandy Bridge microarchitecture doesn’t go anywhere during overclocking. Even when we push our Core i7-2600K to its maximum of 4.7 GHz, the system with this processor still consumes less power than the Core i7-990X Extreme Edition based platform working in nominal mode.