iMac 21,5 2010 - Need help on GPU Upgrade | MacRumors Forums
How to upgrade a Mac: Swap in new RAM, graphics card, hard drive and more | Macworld
Original Graphics Video Card Replacement for Apple iMac Core i3 3.2 Mid-2010 21.5 Inch Desktop Computer A1311 MC509LL/A MC509, AMD ATI Radeon HD 5670 GDDR3 512MB, GPU Board Repair Parts : Electronics