iMac with 64/128 GB RAM - (2 x 32GB) or (4 x 32 GB)

geo.

macrumors newbie
Original poster
Apr 1, 2019
12
3
Hi!

It seems the guys from OWC installed 128 GB RAM on the iMac 2019 which is pretty cool! Does anyone used RAM modules of 32 GB? Apple says it can support up to 64 GB (4x16 RAM), but I don't know the reason why they limited it.

I'm planning to upgrade the RAM for a new iMac 2019 (for now 64 GB), so my concern is if the iMac can support without issues 32 GB modules. That's because perhaps I would like to upgrade to 128 GB in the future and I would like to take the correct decision now. So I think I have this options:
  1. Buy 4 x 16 GB = 64 GB RAM (not ideal if later I want to upgrade to 128, I have to buy again new RAM)
  2. Buy 2 x 32 GB = 64 GB RAM (and perhaps use the existing 8 GB RAM, since we have 2 empty slots - 64 GB + 8 GB = 72 GB RAM)
Also, could be any issues if we mix 32 GB modules with 16 GB modules or others? And lastly, any recommendation which brand to buy?

Thanks a lot!
 

RyanXM

macrumors 6502
Jul 7, 2012
333
352
DFW, TX
I have a 2019 i9 with 128GB (4x32GB) and it has been running flawless for 4 days. I did run the Extended Diagnostics (hold D at startup, once it finishes the short test, CMD+E) and it passed with flying colors.

I'm using Samsung OEM as they are easy to get for me. There are 32GB SK Hynix and Micron SO-DIMMs popping up in the marketplace, but aren't all that easy to find.
 

geo.

macrumors newbie
Original poster
Apr 1, 2019
12
3
I have a 2019 i9 with 128GB (4x32GB) and it has been running flawless for 4 days. I did run the Extended Diagnostics (hold D at startup, once it finishes the short test, CMD+E) and it passed with flying colors.

I'm using Samsung OEM as they are easy to get for me. There are 32GB SK Hynix and Micron SO-DIMMs popping up in the marketplace, but aren't all that easy to find.
Thanks for your information. So it seems it's safe to install 32GB modules. You are right, at this moment it's hard to find them. I guess the only right place to look it's OWC. They sell this module:

https://eshop.macsales.com/item/OWC/2666DDR4S32G/

But I worry about their specs, doesn't match exactly Apple specs (https://support.apple.com/en-us/HT201191#27inch2019):

Apple specs:
  • PC4-21333
  • 260-pin
  • 2666MHz DDR4 SO-DIM
OWC specs:
  • PC4-21300
  • 260-pin
  • 2666MHz DDR4 SO-DIM
As you can see there is a difference for PC4. Would this difference have any incompatibility/performance issues?

Thanks.