2017, 27-inch Retina 5K iMac - 128GB Ram Upgrade

Hexley

macrumors 6502a
Jun 10, 2009
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Curious, for those running on 128GB of RAM what's your use case?

I am thinking of getting 2x32GB and also use 2x4GB that came with the iMac Core i9 for a total of 72GB of RAM
 

Zdigital2015

macrumors 68020
Jul 14, 2015
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East Coast, United States
Curious, for those running on 128GB of RAM what's your use case?

I am thinking of getting 2x32GB and also use 2x4GB that came with the iMac Core i9 for a total of 72GB of RAM
Given the 6- and 8-core CPUs in the iMac, the use case can be as varied as Virtual Machines for developers or video editing, whereas 8GB per core is sort of a good rule of thumb for VMs, plus 8-16GB DRAM for macOS.

Video editing can benefit to an extent although most video editing apps are perfectly satisfied with 32-40GB of DRAM and there are less benefits but you can certainly have FCP X and Motion open at the same time with out feeling as much of a slow down.

Lots of virtual instruments in your DAW will benefit as well.

Given the relatively low cost to add 128GB to a 2019 iMac, around $500 now, it’s definitely a way to future proof your DRAM needs.
 
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Hexley

macrumors 6502a
Jun 10, 2009
990
72
Given the 6- and 8-core CPUs in the iMac, the use case can be as varied as Virtual Machines for developers or video editing, whereas 8GB per core is sort of a good rule of thumb for VMs, plus 8-16GB DRAM for macOS.

Video editing can benefit to an extent although most video editing apps are perfectly satisfied with 32-40GB of DRAM and there are less benefits but you can certainly have FCP X and Motion open at the same time with out feeling as much of a slow down.

Lots of virtual instruments in your DAW will benefit as well.

Given the relatively low cost to add 128GB to a 2019 iMac, around $500 now, it’s definitely a way to future proof your DRAM needs.
Thank you for taking the time to answer.

The often referenced Samsung M471A4G43MB1 32GB DDR4 2666MHz SODIMM was selling at its lowest price of $112.75 last December. Other brands have it near $100. So 4 of them would cost $400-451 for 128GB of RAM. Mind boggling amount a few years ago.

The 2017 iMac 27" can only show 128GB of RAM but cannot use more than 64GB. So best way to handle this would be to put 2x32GB then sell or set aside the original 2x4GB that came with the iMac.
 
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Hexley

macrumors 6502a
Jun 10, 2009
990
72
Why does macOS' "Activity Monitor" show 75.5GB "Memory Used?

Under Windows 10 it's clear cut that 64GB is only usable.

At idle my Wired Memory is 1.85GB while my Physical Memory is 32GB.

I received the 128GB RAM today, installed and the Mac can see the 128GB RAM but cannot use it just as I suspected. Both Bootcamp (Win10) and the very latest Catalina update today does not allow more than 64GB to be used on this 2017 5k 27inch i7-7700k 4.2 turbo 4.5 Mac.

If you are wanting/thinking of doing this upgrade do not waste your time, effort or money (if not returnable). If someone says it does they are wrong. OWC did a 128GB install on a 2019 Mac and showed proof that not only did that Mac see but also could use the full 128GB installed. The Wired Memory info in Activity Monitor is the proof along with Atomic software RAM test.

My wired memory is 67.78GB. That is all the proof you need to see that your Mac cannot use all the Physical Memory installed. In my case 128GB. I can only use 64GB RAM not the Physical of 128GB which was installed. I knew going in that Kaby Lake i7-7700k shows only 64GB supported but others in this forum said it can use 128GB because it worked for them. There is no possible way it did work unless I'm missing something which is unlikely.

I would love for these to work, that is why I bought them but for others to say they tested extensively and works 100% is not true. I welcome anyone to show proof of this particular Mac to actually work with 128GB and not just show it can hold 128 GB. Like I said, I would keep them if in fact they worked but sadly they do not and are being returned.

Most likely I hear crickets when it comes to anyone showing proof they work. That is why OWC doesn't sell 128GB RAM upgrade for this model. If it could work they definitely would be selling it. I knew this going in but was willing to try installing them since others have said it worked 100% and they tested extensively. I hope I'm wrong but unlikely at this point.

See pics below.

View attachment 869775View attachment 869776