Turbo Mode

Overclocking goes mainstream with turbo mode

Turbo Mode overclocks some of the processing cores of Nehalem if other cores are shut down. The typical example given by Intel is of a quad-core Nehalem CPU. If the third and fourth cores are idle, the advanced power management of Nehalem will shut them down.

This means that the CPU as a whole will produce far less heat than its rated TDP (Thermal Design Power) implies. With the spare thermal headroom, Nehalem will overclock the processing cores being used to provide extra speed if your application only uses a single thread. No software is needed to take advantage of this, though Intel did confirm that it’s possible to disable Turbo Mode in the BIOS, as long as the motherboard maker has included the option.

If the application uses two cores of a four-core processor, the cores being used will overclock by one ‘tick’. If the application you’re using is single-threaded, Nehalem will overclock a single core by two ‘ticks’. Nehalem’s internal clock runs at 133MHz, so each ‘tick’ should equate to an extra 133MHz.


Turbo Mode isn’t a new technology, as laptops featuring the Santa Rosa revision of Centrino also used the technology. However, as the processors used in these laptops are dual-core the effects are less marked. The power saving from the Power Gate technology also allows Turbo Mode to be more effective on Nehalem.

One potential issue with Turbo Mode is that Windows already does a good job of load balancing across multiple CPU cores. Watch a quad-core PC idling in Task Manager and you’ll see small blips of processor use from all four cores at different times. Without knowing further details, it seems possible that in some situations a Core i7 CPU may sometimes be unable to take advantage of Turbo Mode, even if its cores are mostly idle.

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