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Does a 8GB PC3-12800S 1600MHz DDR3 supported if I want to upgrade my iMac 21.5 late 2013. Mine is an entry level spec.
Two 8GB PC3-12800S 1600MHz DDR3 SO-DIMMs will get you to 16GB. Your system currently has two 4GB PC3-12800S 1600MHz DDR3 SO-DIMMs which you can see by going to the Apple Menu > About This Mac, going to the Memory tab. As an example here’s my system:
