I just purchased an iMac 27" retina 2019 and it came with preinstalled 8GB memory. It has two empty slots. Can I add two 8GB memory modules and keep the 4GB modules to increase the memory to 24GB or do I need to remove the 4GB modules and just have 16GB instead?
iMac 27", macOS 10.15
Yes you can keep the 8GB and install a matching pair of modules in the empty slots.
However Mac's are picky and your best bet, is to buy RAM upgrades directly from either OWC or Crucial.
https://eshop.macsales.com/shop/apple/memory/iMac
https://www.crucial.com/usa/en/compatible-upgrade-for/Apple/imac-%28retina-5k%2C-27-inch
Yes you can keep the 8GB and install a matching pair of modules in the empty slots.
However Mac's are picky and your best bet, is to buy RAM upgrades directly from either OWC or Crucial.
https://eshop.macsales.com/shop/apple/memory/iMac
https://www.crucial.com/usa/en/compatible-upgrade-for/Apple/imac-%28retina-5k%2C-27-inch
Yes, absolutely no problem. I intend to do the same thing when I order my new machine with 8GB, I will be adding 2x16GB of RAM to upgrade to 40 GB of RAM. Just install the new RAM in the empty slots and you are all set!
You can mix them.
No. Those should be identical.
Speaking of OWC RAM, see: Ram for 2019 iMac (19,1) - Apple Community
Had to say for sure if that is a bad module, an improperly seated module or the RAM controller... I remember a similar problem years ago when folks were installing a matching set of 4 modules in the 24" models. They would try all different tests and configurations. It worked fine with 2 factory and 2 new modules or just 3 new modules, it even worked with 1 factory and 3 new modules, but it just would not work with all 4 modules from a matching set.
The Apple Installing Memory Support article say's PC4-21333 and the vendors are selling PC4-21300. The only thing that I can think of at this point, is that it is a typo in the Apple Installing Memory article.
8+2x16=40. Good to know. 😎
That plus the RAM modules folks are selling for 2019 iMacs are not the exact specs Apple lists. I forget the difference off the top of my head.
Would that be the PC4-21333 vs PC4-21300 thing?
Can I mix 4GM and 16GB memory
