Enhancements for Mobile CPUs

Penryn Core brings two new features for mobile CPUs: Deep Power Down Technology and Enhanced Dynamic Acceleration Technology.

Deep Power Down Technology

In order to save power, Intel mobile CPUs can reduce their voltage, disable their clock and even disable their memory cache when they are idle. This is particular useful in laptops, where any savings in power translates into a longer battery life.

There are three basic power-saving modes, called Halt (or C1), Stop Clock (or C2) and Deep Sleep (or C3). When no power saving mode is being used, the CPU is fully active and it is said to be in its C0 mode. These power-saving modes are generically called C-states.

With the first dual-core CPU based on the Pentium M core, called Core Duo, Intel allowed these modes to be configured on a per-core basis, meaning that if one of the CPU cores are idle, the CPU can reduce the voltage and turn off the clock for this core, while the other core is fully active. So the two cores can be on a different C-state. Also with this CPU Intel introduced two new C-states, Deeper Sleep (C4) and Enhanced Deeper Sleep (DC4), which can only be activated for the two cores at the same time.

Penryn core brings a new C state, called Deep Power Down (C6). When the CPU enters this mode, the CPU voltage is reduced a lot, the clock signals are disabled and both memory caches are turned off. This mode saves more power (i.e. battery) than all other C modes available to date, but on the other hand the CPU delays more to go back to work at full speed.

On Figure 5 you can see a comparison of the new Deep Power Down mode to the other C- modes currently available on Core Duo and Core 2 CPUs.

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Figure 5: Deep Power Down mode compared to other C-modes.

This new C mode is only available on mobile CPUs.

Enhanced Dynamic Acceleration Technology

When one of the cores enters one of the deeper power saving states (C3 state on) the new Penryn core allows the other core to increase its core clock (i.e. to overclock itself) keeping the CPU inside its TDP (Thermal Design Power). Since the inactive core will be consuming less power, the active core can dissipate more heat and consume more energy and still maintain the CPU inside its thermal and power envelope: the whole CPU will still be consuming the same amount of energy (or less) and be dissipating the same amount of heat (or less).

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Figure 6: Enhanced Dynamic Acceleration Technology.

Like Deep Power Down, this new feature is only available on mobile CPUs.

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