Intel Core i7 Mobile CPU (Clarksfield) Review

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Intel Turbo Boost Technology



Intel Turbo Boost Technology has been part of the Core i7 (Nehalem) architecture from day one. However, Lynnfield and Clarksfield bring a significant update to the Turbo Boost technology, making it an even more flexible and powerful performance booster.


A graphical example of how Core i7 Mobile Turbo Boost works.

The Core i7 Mobile processor is actually capable of three different speeds above its base speed, depending on the nature of the active single or multi-threaded workloads (and as long as the processor is operating within specified thermal and power limits). When a single-threaded workload is detected, the Core i7-920XM's clock speed on just a single execution core increases up to 3.2GHz, while the remaining three cores remain inactive and operate and close to zero power. When a lightly-threaded workload is detected, only two cores are active and they operate at up to 3.06GHz. With a high-threaded workload, all four cores are active and operate at up to 2.26GHz.

 
A single-threaded workload (left) vs. a heavily-threaded workload (right).

The image on the left was recorded while Cinebench R10 was running its single-threaded workload. As you can see in Windows 7's Resource Monitor, CPU2 is getting pegged heavily. There is also some activity on CPU1, CPU5, and CPU7, which can be attributed to Windows 7 background tasks and other apps running in the background. The Intel Turbo Boost Technology Monitor gadget shows the processor running at 3.2GHz. While this screenshot shows that the Core i7-920XM is capable of scaling up to 3.2GHz, the chip actually ran at 3.07GHz during the vast majority of the test run.

The screenshot on the right was captured while Cinebench R10 was running its multi-threaded workload. Resource Monitor shows all four physical execution cores and all four Hyper-Threading virtual cores completely saturated, with the Intel Turbo Boost Technology Monitor showing the processor running at 2.0GHz. Curiously, the processor did not run at the 2.26GHz speed that Turbo Boost supports for highly-threaded workloads, and instead ran at the processor's 2.0GHz base speed.


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