Well, performance is not the single important characteristic of a mobile processor – users are interested in low power consumption, too. When developing the Core Duo, Intel tried its best to make it at least no worse than the Dothan-core Pentium M as concerns power-related characteristics. The dual-core architecture by itself opens numerous power-saving opportunities and the developers were eager to catch at them. New in the Core Duo, Intel Dynamic Power Coordination technology allows to adjust the power-saving parameters of the execution cores independently. So when multi-threaded processing is not necessary at the moment, one execution core can be turned off to reduce the heat consumption and heat dissipation of the whole processor. With Dynamic Power Coordination, a processor core can be switched into reduced power consumption states: Halt, Stop and Deep Sleep. The processor also features two even more economical states for idle modes – Deeper Sleep and Enhanced Deeper Sleep – but they can only be activated for both the cores at once.
Surely the new dual-core processor supports Enhanced Intel SpeedStep technology (EIST) that we’ve got used to see in any CPU from Intel. The technology allows adjusting the CPU clock rate and voltage “on the fly” depending on the current load, but it affects both the cores at once, too. The minimum frequency the Core Duo can work at with enabled EIST is 1GHz irrespective of the default clock rate of the particular CPU model.
The Core Duo’s pack of power-saving technologies is quite efficient as is illustrated by the fact that the maximum power dissipation of the new processor is 31W which is only 4W higher than that of the Dothan-core Pentium M. But the Core Duo has two execution cores rather than one! The average power consumption of the new processor under normal conditions, i.e. at everyday work, is roughly the same as of the single-core predecessor. It means your notebook with a Core Duo inside is going to work nearly as long on its battery as an analogous notebook with a Dothan-core Pentium M.
These facts are impressive and even hard to believe in until you learn of one more technology that complements Smart Cache and Dynamic Power Coordination. This technology allows to adjust dynamically the size of an active portion of L2 cache memory, turning off unused sections. This makes sense considering that the L2 cache accounts for about 35-40% of the total area of the Core Duo chip. It works like this: when the Smart Cache logic finds that some section of the cache memory hasn’t been accessed for a specified period of time, the data from this section are sent to the system memory and the section itself is powered off. By the way, it is this algorithm that makes possible the additional power-saving state Enhanced Deeper Sleep available with the Core Duo. The min voltage level in the Deeper Sleep mode depended on the necessity to keep up the cache memory, but now this is not necessary since data from the L2 cache is transferred into the system memory and the cache itself is turned off when the CPU is idle.