128 GB Ram Useable/Beneficial on New 2019 27 inch iMac?


macrumors newbie
Original poster
Mar 23, 2019
Hello, 64 GB is the maximum RAM one can use in the new 2019 5k 27" iMacs according to Apple.

I read that these machines can "read" up to 128GB ram tho. Is this a "thing"?

I have never heard of stuffing a machine with more Ram than spec'd before.

Is outfitting these with 128GB of Crucial or OWC Ram worthwhile? Can the computer even effectively make use of the extra 64GB ram?

Are there compatibility, stability, accelerated wear and tear on this imac if you stuff it with extra Ram beyond its specs?

Experienced/Educated input appreciated.

Thanks in advance.


macrumors 604
Aug 17, 2007
Seattle, WA
128GB could be usable if you run a shedload of Virtual Machines.

Otherwise, I would think that if you are running applications that could significantly benefit from 128GB of RAM, they can probably benefit from the Xeon CPU and better Vega GPUs of the iMac Pro.

And the iMac Pro might be better for multiple VMs since you can get it with significantly more CPU cores.
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macrumors G4
Jun 27, 2007
Central U.S.
My 2008 MacBook Pro was spec’d to 4GB max and it took 6GB without issue. It’s been awhile since I’ve had a Mac with user replaceable RAM because I had MBPs which were soldered.

The Intel chips, at least in the i9 specs I looked at, showed the CPU supports 128GB. But you would need four 32GB modules to test, which is very expensive, and there aren’t many options available yet. I’d say this is probably your best bet unless Crucial is selling some on another site: https://smile.amazon.com/Mushkin-Essentials-PC4-21300-Low-Voltage-MES4S266KF32G/dp/B07MZCCMHY. Apple could also potentially block more than 64GB on boot using firmware.

Personally I’m going to end up with 40GB in mine and probably upgrade to 64GB in a few years when it’s pretty cheap. I can’t see needing more than that for my use case within 7-8 years.