With the release of the new Sandy Bridge-equipped MacBook Pros, users have been expecting clockspeeds of up to 3.4 GHz with Intel Turbo Boost technology. However, it at least a couple
, 13" models with Core i7-2620M processors have been reported to stall out at 2.7 GHz when using Windows. The culprit may be high core temperature, which is not being seen when the 13" is running Mac OS X or at all in the larger models. Other tests show the 13" performing as advertised
. So what's going on here?
Intel upgraded Turbo Boost to take better advantage of the Sandy Bridge microarchitecture on its latest Core Series chips. Like the original algorithm, version 2.0 of the dynamic overclocking feature lets operating systems request more power when power consumption and temperature are below preset limits for the number of active cores, and likewise underclocks when those limits are exceeded. PC Pro
's testing showed that the Core i7-2620M in their 13" late 2010 MacBook Pro remained at the rated 2.7 GHz under Windows testing, but temperatures spiked to 93°C or about 200°F. A similar test by Notebook Journal
in Germany actually showed the processor underclocking itself to 798 MHz under load.
At the same time, Anand Shimpi tested the 13" Pro against his usual Mac OS X SYSMark suite, and found that it was able to boost up to 3.4GHz
in single core mode, and 3.2GHz for dual core. His reported core temps went up to 94°C when the machine boosted in dual core, indicating that the temperature threshold should not have been the bottleneck for PC Pro. Indeed, in a later update, PC Pro found that Turbo Boost worked properly under Mac OS X, at higher temperatures than it reached un-Boosted under Windows.
PC Pro speculates that Apple disabled Turbo Boost on MacBook Pros running Windows, or blocked those operating system calls from being sent to the processor, for reasons of heat dissipation. They also noted temperatures spiking up to 99°C core, with the underside heating to a painful 60°C or 140°F. Until this is resolved definitively, users interested in running Windows on the smallest Pro should hold off on purchasing.
Source: Product Reviews