I nearly had one of that configuration back in August, just before buying this iMac. I was contemplating the replacement of a 4 GB stick of RAM with one of 8 GB in a 2011 MacBook Pro with an SSD installed. It had 12 GB of RAM & I was thinking of going up to 16 GB.
But the motherboard interface with the video card died the very next day. That it for such a Mac: it was the first Mac to use tin-free solder & they didn't get it right. It was a known error, Apple offered a free fix up to five years after the purchase date of the thing: replace with a pre-used motherboard. Mine hadn't shown any problems so I didn't bother with the repair. It was 6½years old at its demise.

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