News Case Of Underclocked GPU On MacBook Pro

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Apple appears to have underclocked the ATI Radeon Mobility X1600 graphics chip in its MacBook Pro laptop. According to one online report, the GPU's core runs 35 per cent slower than the clock speed recommended by ATI.

Apple's MacBook Pros, which replace the PowerBook family has been receiving a lot of press too. The laptops themselves are great performers and best even the fastest available Windows notebooks on the market in many areas. Many MacBook Pro users have installed Windows XP and discovered that Windows XP runs extremely well. The MacBook Pro is the only notebook available that is able to fully run Apple's OS X and Windows XP natively.

The speed differential was spotted by a poster on French-language site MacBidouille, the site reports. The correspondent ran ATI's ATI Tools utility - version 0.25, a beta release - running under Windows XP. The software revealed his MacBook Pro's X1600 was clocked at 310MHz and the memory at 278MHz (556MHz effective).

MacBidouille repeated the process and confirmed the numbers, adding that ATI recommends system vendors run the GPU with a core frequency of 475MHz and setting the memory clock to 470MHz (940MHz effective).

No artifacts or abnormal behavior was noticed and some have said that they've noticed significant frame rate improvements after the Radeon X1600 was set to its normal specifications.

It is speculated that Apple has declocked the GPU and its accompanying memory in the MacBook Pro to conserve battery power as well as to reduce the amount of heat generated. Upon removing the clock rate cap, users have discovered that the MacBook Pro's internal fans spin up much more noticeably and battery life reduced by roughly 30 minutes. In a notebook that only lasts roughly 3 hours, 30 minutes is a lot of time.

The report warns that ATI's code is rather unstable - it is a pre-release version, after all - but it does indicate there's room to speed up the notebook's GPU at the cost of a much more noisy fan.

The gain that's possible? According to the forum poster, who followed up his initially finding by installing "ATI-optimised drivers" rather than the ones supplied by Apple, his Counter Strike benchmark test with all settings pushed to the max and the resolution set to 1,440 x 900 saw frame rates jump from 61 to 97.

Of course, that's under Windows XP - it remains to be seen how Mac OS X users can gain the same benefit
 
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