June 7, 2006 2:00 PM PDT

MacBook Pro Special Report: Clock speed of ATI X1600 card -- some units apparently underclocked

by CNET staff

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As first reported by the French Web site MacBidoulle, the ATI X1600 graphics card included with MacBook Pro 15.4" models is clocked at at 310Mhz for the GPU and 278Mhz for the graphics RAM. The card can actually be clocked significantly higher, and set at 470 MHz for the GPU and 470 MHz for the graphics RAM in some other notebook computers.

Users can overclock the ATI X1600 card (above Apple's default settings) using the utility ATI Tool while booted into Windows XP (a Mac OS X utility for overclocking does not yet exist). NOTE that we have not yet determined whether or not this process will violate your Apple warranty, though the company could certainly claim exemption from liability for damage resultant from heat generated by this modification, per the warranty agreement included with the MacBook Pro and Intel-based iMac.

Users who have overclocked the cards are reporting real-world performance gains commensurate with the clock increase -- generally in the range of 20-25%.

Note that the settings you enact will only remain for the current session. After you restart, the settings will revert back to the default (310/278 MHz) settings. If you boot back into Mac OS X, the default settings will also return.

The maximum stable clock speed at this point appears to be 430.07(GPU)/468.00(RAM).

If you have problems overclocking at first, make sure the 3D window is closed (using the 'Close 3D View' button) before applying the changes.

If you do decide to overclock, make sure you have a utility like Temperature Monitor handy. Check various temperature readings before changing clock settings, then track how those temperatures change after the up-clocking process. If there are significant increases, it's probably a good idea to restore the original settings.

Also, make sure your MacBook Pro is plugged in when attempting overclocking.

However, some users also report significantly increased fan activity and surface heat temperatures after up-clocking their systems. Some users also report repeated crashes when using the higher clock speeds.

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