How to Upgrade iMac Hard Drive (2009, 2010, 2011): EveryMac.com
Apple Mac Desktop Benchmarks (Intel): EveryMac.com
How do the "Mid-2011" Aluminum iMac models compare to the "Mid-2010" models that preceded them?: EveryMac.com
Identify your iMac model - Apple Support
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How to Upgrade iMac Hard Drive (2009, 2010, 2011): EveryMac.com