24GB RAM in Retina iMac - Matching?


macrumors regular
Original poster
Dec 22, 2004
Hi all.

I purchased a Retina iMac 5K and have basically tricked it out - 3TB Fusion, CPU upgrade, GPU upgrade. I have however ordered it with stock RAM with the intent of upgrading it using third party RAM.

My question is this. Will buying a 16GB kit (2 x 8GB) and installing that alongside the existing 8GB (2 x 4GB sticks) be non-optimal? Is it better to have a machine with all the same sized sticks or does it not matter as long as you have matched 'pairs'? I may in time upgrade to 32GB, but at this stage I'd like to give 24GB a whirl and save myself some money after what is quite an expensive purchase.

Insight appreciated!


macrumors 6502
Jun 4, 2012
Yup, 24GB is fine as long as the modules are matching pairs. Just fill in the remaining sockets when you receive the machine and it will work perfectly. Just don't place them side by side module A, B, but A, C.