Original URL: http://www.theregister.co.uk/2011/03/22/mac_book_pro_turbo_boost/

Testers show MacBook Pro Turbo Boost oddness

It works! Oh no it doesn't! Oh yes it does! etc, etc.

By Tony Smith

Posted in Laptops, 22nd March 2011 09:16 GMT

Some unexpected benchmark results may show how Apple is implementing - or not - a key feature of Intel's second-generation Core i platform, 'Sandy Bridge'.

Tests performed by dead-tree title PC Pro show that Sandy Bridge's Turbo Boost technology, which dynamically overclocks one, two or four cores based if the CPU load could use it but holds back if the thermals show this would be a bad idea, isn't always enabled.

The mag tested Core i5- and Core i7-based - both two-core chips - 13in MacBook Pros running Windows 7 with Apple's Bootcamp multi-OS system, and found that Turbo Boost works on the former, but doesn't on the latter.

Website Anandtech provides corroborating evidence that the Core i5-based 13in MBP uses Turbo Boost when possible, in both Windows 7 and Mac OS X.

The odd thing: the Core i7 Turbos under Mac OS X too, so it's only under Windows that the feature is seemingly disabled.

Conspiracy seems unlikely - if Apple was trying to ensure Windows performed less well on these machines, it would surely disable Turbo Boost on the Core i5 MBP too.

In any case, delivering good Windows performance is a sensible move for Apple: it helps convince PC owners to migrate to Mac by showing they won't lose horsepower if they do.

If the reason was related to system thermals, you'd expect the quad-core MBP to stop Turbo Boost in both OS X and Windows 7, not just the latter.

The 15in MBP, all versions of which use the Core i7 - and a quad-core one, to boot - and there's no reduction in Turbo Boost performance, Anandtech's tests show.

The question is, is PC Pro's odd result the sign of a one-off machine problem, an issue with that particular CPU - the dual-core 2.7GHz Intel Core i7-2620M - or a glitch in the Core i7 family?

Recent reports of 15in and 17in MBP freezes under heavy CPU and/or GPU Load show some machines are thermally challenged - though where through excessive use of thermal paste, problematic logic boards or some other reason, isn't yet clear. ®