Review on 🖥️ Adamanta 16GB (2x8GB) Apple Memory Upgrade for Late 2015 iMac 27" Retina 5K Display DDR3/DDR3L 1867Mhz PC3L-14900 SODIMM 2Rx8 CL13 1.35v RAM DRAM - Enhanced SEO by Christopher Williams

The only thing that confuses when installing this memory is which of the slots to install pairs in. Instructions for installing memory banks are included with the memory. If you open an Apple iMac you will see DIMMs in slots 1 and 3. Based on the customer pictures uploaded to Revain it seems most people add their new DIMMs in slots 2 and 4. The included instructions memory call for installing genuine Apple memory in slot 1 and slot 2 and new memory in slot 3 and 4. In this configuration, BANK0 has 2 x 8GB and BANK1 has 2 x 4GB. I've tried both configurations and the iMac starts up fine and shows 24GB. I ran Novabench to see how fast the memory was. I'm still not quite sure how best to do this. Based on the pictures people have uploaded, most people get it wrong, but it's not an experience issue.