The GPU: Faster - Apple 15-inch MacBook Pro (Late 2011) Review
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The GPU - The 27-inch Apple iMac Review (2011)
Apple MacBook Pro range refreshed with faster processors - CNET
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Graphics card HD 6770M Ati Radeon HD6770 for iMac 21.5" and 27" 512 MB.
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For iMac A1311 21.5" Mid 2011 AMD Radeon HD 6750M 512MB Upgrade Nvidia K1100m 2GB GDDR5 Video Graphics Card MC309LL/A MC812LL/A Gadgets - Newegg.com