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2017, 27-inch Retina 5K iMac - 128GB Ram Upgrade
- Thread starter rxs0
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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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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.
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.
Cool,
I amgoing to upgrade my 4k (2 memory slots) and I will chose kingston module 2x32Gb for a total of 64Gb,unofficially supported, as I can nsee, did you have any problem with 2666 modules?
Hi, I find this fascinating and would like to do the same for my 27" iMac. Being in the UK i cannot get the modules you used but, Amazon UK have these:
Samsung 32GB DDR4 2666MHz RAM Memory Module for Laptop Computers (260 Pin SODIMM, 1.2V) M471A4G43MB1.
1) Do you think they would do? and2 DO I simply need to remove the current 64Gb and stick in four of these?
Thanks very much, Richard
The "Wired Memory" of 67GB is the clue that 64GB of the 128GB RAM cannot be used. Usually wired memory (i.e., system reserved memory) should be only about 3GB. That it reports about 67GB wired memory means that it is effectively "reserving" 64GB of the 128GB RAM as inaccessible for user or app use.
I ordered a 2667 MHz 64 Gb upgrade for my 2017 27" iMac. I had 32 Gb 2400 MHz memory. My plan is to go up to 128 Gb in the future. With this upgrade, I had 4 ~ 8 Gb simms and 2 ~ 32 Gb simms. This allowed me to decrease the memory installed from 80 Gb to 8 Gb in 8 Gb increments.
What I found is that when the memory was above 64 Gb, both MacOS and Windows 10 were using the full memory installed - above 64 Gb. MacOS has several ways to allot memory. There is memory allotted to Apps only (permanent) and the OS only ("wired memory" - permanent). Of what's left unused, MacOS will use a portion of that to cache programs not in use.
In my testing, I started loading Pages, Numbers and Keynote apps. I quickly found those barely touched the amount of memory installed. I then loaded up Books, Store, System Settings, Weather, Free Form, Maps, Preview, Photos, Reminders Notes and Mail and still hardly touched the memory. I opened two more instances of Pages, Numbers and Keynote. Still not close. I opened up Asphalt 9 and got a race going and the memory used jumped up. I also had some monitor software running. I then opened 8 YouTube videos in Safari with 4k or better videos playing at 2160P quality. This took my total memory usage up over 64 Gb and an available memory usage below 16 Gb.
The Mac is using all the memory installed. I did try to determine if there was an advantage go using the faster memory and could not determine that. 2400 vs 2667 is not a significant difference. 32 Gb simms of 2400 and 2667 memory are roughly the same price.
Throughout my testing, I reduced the memory by 8 Gb. The Mac ran the same as far as memory management goes between 80 Gb to 64 Gb. App, Wired and Cached memory were about the same. At 80 Gb I had 14.4 Gb available. At 64 Gb, I had 1.4 Gb available. At 56 Gb, I had to shut down one Youtube video to get the others to play without a wait timer. Also at 56 Gb, the Wired memory usage dropped by almost half. I suspect MacOS began to control the memory available to the Apps. At 56 Gb I had about 17 Gb available. At 48 Gb the available memory dropped to 11.5 Gb.
Then at each of the 40 Gb and 32 Gb iterations, I had to close down another video to maintain an available memory at over 5 Gb and to keep the remaining videos playing. The drop to 32 Gb also reduced the Wired Memory again by just under half, while the Apps and Cache stayed the same.
At 24 Gb the apps, wired and cache began getting less memory and the available memory pretty much dropped into the 100 Mb range. At 16 Gb, a fourth memory allocation began being used. Compressed memory - where programs that are not being used are compressed in RAM to save space. Also HDD/SDD space began being used for swap in the 100's of Mb. The videos still played but with significant lag. At 8 Gb, the videos would not play and the swap drive usage went over a gigabit.
My feeling is when the memory is 64 Gb or over, the system is running efficiently without the need for calculating memory compression or swapping to a drive. You are also saving wear and tear on your SSD. Your system run well between 24 Gb to 64 Gb for the same reasons, however there are limits set in the OS for the system and apps.
As for Windows, what one sees in the About box for what is available vs. installed, Windows takes a substantial amount of memory - if available for the system and graphics shared memory. At 80 Gb, I was able to account for over 70 Gb between locatable memory and system reserve (of which about 20 GB was allotted to shared graphics.
The charts attached shows the memory allotment at each 8 Gb iteration.
Below, I have provided a screenshot of the cycle at 80 Gb. Add the Memory Used and Cached and you get the memory used above 64 Gb.
it is quite possible that imac pro can accept this frequency
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.
![Win10-RAMpic.PNG]( "Win10-RAMpic.PNG")
![Screen Shot 2019-10-15 at 4.30.19 PM.png]( "Screen Shot 2019-10-15 at 4.30.19 PM.png")
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.
I proved that I could use all of the 80Gb memory I installed. In my testing, I was using Sonoma.
In your example above, you are also using more than 64Gb. Your apps are using 7.75 Gb and your system and data outside of apps is using 67.75. These are added together to determine the total memory your system is using (without cache and compressed memory (75.5 Gb). You are also using an additional 4.42 Gb for cached files in RAM. In the snap shot above your system is using a total of 79.92 Gb out of the 128Gb.
In your windows partition, open the task manager and open the memory usesage tab. You will see system use (which includes graphics) is taking up the memory available beyond the 63.9 Gb. What you posted above is showing me that your system is using all of the 128 Gb. There are a good number of YouTube videos that explains how macOS manages memory.
In learning about memory use in macOS, 16 Gb is the minimum I'd recommend to stay out of swap and compressed memory (both degrade performance on intel based Macs.). 32 Gb provides marginally better performance. Above that for normal use literally didn't make any difference. If you are producing large 4K videos or compiling large programs, you may use your full memory you installed. For normal use, 32 Gb to 128 Gb will look and feel the same.
I did some additional research on this. Yes, the "Wired Memory" allots memory macOS does not want to provide to the OS or Apps. The issue in my example above is a jump in size occurred between 32 GB and 64 GB. The machine allows 64 GB. Another jump did occur at 64 GB as well. In one explanation, this allocation occurs when there is an incompatibility of hardware (ssd, memory DIMMs, etc). So I have to get back to the drawing board on this project. If MacOS is allocating memory that is unusable by the CPU (memory above 64 GB), the massive increase of "Wired Memory" should have occurred after the 64 GB point (at and after 72 GB) , not at or before 64GB. In Windows 10, the surplus memory went to Graphics (as reported by the task manager). I will revisit this and report back in a few weeks. Information on what is included with "wired Memory" is anaemic and extremely varied.
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What are your results (as presented above) if you only have 64 Gb in the system? If you subtract 64 from your Wired Memory, you have 3.75 GB being used by the system and 64 GB being locked out. 3.75 GB is within the realm of possibility of actual system use. In my experimenting, my Wired Memory jumped up when I installed 32 GB and above. Since my system is spec'ed for 64 GB, I should not have had any jump in Wired Memory until I installed 72 GB. From some things I read, my particular jumps could be because I installed incompatible RAM.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.
![Win10-RAMpic.PNG]( "Win10-RAMpic.PNG")
![Screen Shot 2019-10-15 at 4.30.19 PM.png]( "Screen Shot 2019-10-15 at 4.30.19 PM.png")
I will have to concede that the memory in excess of what is specified for the 2017 27" iMac is being consumed by wired memory. My problems with memory allocation may have been caused by mixing 2400 and 2667 memory. This time I started with 8 Gb and worked up to 32 Gb in 8 Gb increments with the 2400 MHz memory. I then worked up from 32 Gb to 96 Gb in 16 Gb increments with the 2667 MHz memory. The Wired Memory slowly increased from 2.25 Gb to 5.19 Gb (5 8k videos playing in separate Youtube tabbed safari tabbed windows, a pages, numbers, keynote documents open and the Apple Store open - same app set at each increment) from 8 Gb to 64 Gb RAM. When I added the final 32 Gb the wired memory jumped to 36.92 Gb. Remove the 32 Gb, the Wired Memory would be 4.92 Gb - right in line with the previous memory levels. With this machine, it does look like adding memory above the specified level doesn't give you more memory, even if the OS recognizes the memory was added.
I have upgraded many machines beyond the specified memory levels. This is the first machine that maintained a hard top limit.
Lots of fun never the less.
Final Thoughts:
My 2017 iMac 27" 5K was working well with all the 96 GB installed. But I took the extra 32 GB out and went with the 64 GB. The machine seems snappier. No data. It just feels snappier with no lag. I am not sure if having the machine manage the blocked memory in addition to managing regular system memory within the Wired Memory creates extra work (I would think so) but it does seem that without the extra memory, things do seem better for me. (Might be a mental thing - who knows).
This machine was originally spec'ed for 32 GB. But found to be able to reach 64 GB. That's a great jump. The limit is due to the i7-7700 CPU as mentioned before. Though the iMac system board can recognize that more memory was installed - above 64 GB, the processor cannot address it. Both macOS and Windows does seem to be able to block out the excess memory. macOS shoves it into Wired Memory. Windows shoves it into the graphics memory - where it will likely never be used.
There is very little information on this. This discussion and experimentations has brought light to this.
If you want 128 GB and an Intel Mac, get the 2019 27" iMac with the better processors.
My 2017 iMac 27" 5K was working well with all the 96 GB installed. But I took the extra 32 GB out and went with the 64 GB. The machine seems snappier. No data. It just feels snappier with no lag. I am not sure if having the machine manage the blocked memory in addition to managing regular system memory within the Wired Memory creates extra work (I would think so) but it does seem that without the extra memory, things do seem better for me. (Might be a mental thing - who knows).
This machine was originally spec'ed for 32 GB. But found to be able to reach 64 GB. That's a great jump. The limit is due to the i7-7700 CPU as mentioned before. Though the iMac system board can recognize that more memory was installed - above 64 GB, the processor cannot address it. Both macOS and Windows does seem to be able to block out the excess memory. macOS shoves it into Wired Memory. Windows shoves it into the graphics memory - where it will likely never be used.
There is very little information on this. This discussion and experimentations has brought light to this.
If you want 128 GB and an Intel Mac, get the 2019 27" iMac with the better processors.
What a fantastic thread! This has essentially answered my curiosity about this topic. Only as a fun project I considered some RAM option upgrades.
I have a 2017 27" iMac 18,3. It's running MacOS 13.6.5 (Ventura), Radeon Pro 580 8 GB, Apple 1TB SSD, 4.2 GHz Quad-Core Intel Core i7. Originally it had 8 GB of 2400GHz DDR4 as 2x4GB. I upgraded it to 64GB with 4x16GB DDR4. No problems. Then I found a sale of Apple Original memory pulls of 2667MHz DDR4 SODIMMS from MacSales.com (OWC). I suspect these were pulled from 2019/2020 Intel iMacs. I bought 4 of them and removed the 4x16GB 2400MHz DDR4 and put the 2667 Mhz in and the About This Mac reported 64GB running at 2667MHz. The iMac was rock solid as I suspect it was running at the spec'd 2400Mhz even though it said 2667MHz. I also considered 128GB but after reading this thread (and I verified my BootCamp partition too) that 64GB is a hard stop limit for this 2017 iMac. That's fine. I don't really need 64GB, much less 128GB.
But what was not addressed as clearly in this thread as I hoped was the speed of the memory. If the 64GB is what is used and more than that is that "macOS shoves it into Wired Memory and Windows shoves it into the graphics memory", meaning 128GB (more than 64GB) is seen but not used, then could the same be true for RAM speed ? That is, if the specification is 2400MHz and some folks show the 2017 iMac using 2667MHz or 3200MHz DDR4, then could it also be that MacOS/i7-7700k "sees" whatever memory speed is spec'd by the DDR4 SODIMs but that in fact it ONLY runs at 2400MHz ?
My system clearly says in both the Windows 10 BootCamp partition and MacOS 64GB DDR4 2667MHz installed. But to be clear, I have not noticed or seen in any usage in Apps or Benchmarks any improvement, however slight with a bumped up RAM speed. I suspect the 2667MHz memory is reported as such but is clocked to 2400Mhz in real use. For that reason I did not bother to see about 3200MHz. My goal was quantity of memory more than speed anyway but I saw the 2667MHz deal and thought why not.
But the question remains. Aside from a hardtop 64GB cap which seems clear on this 2017 iMac, is the same true for SODIMM DDR4 speed ? How do I go about actually testing RAM speed usage? I'm more curious than needing an answer but if true, then while the total RAM cap might be a no-go above 64GB, if the speed is actually a thing of consequence, then perhaps it's worth finding faster RAM instead of more RAM on this iMac? Compatible DDR4 SODIMM RAM faster than 2400MHz does exist so technically it could be an upgrade ? Or is it just what we see, not what we notice in practice?
Any thoughts ?
I have a 2017 27" iMac 18,3. It's running MacOS 13.6.5 (Ventura), Radeon Pro 580 8 GB, Apple 1TB SSD, 4.2 GHz Quad-Core Intel Core i7. Originally it had 8 GB of 2400GHz DDR4 as 2x4GB. I upgraded it to 64GB with 4x16GB DDR4. No problems. Then I found a sale of Apple Original memory pulls of 2667MHz DDR4 SODIMMS from MacSales.com (OWC). I suspect these were pulled from 2019/2020 Intel iMacs. I bought 4 of them and removed the 4x16GB 2400MHz DDR4 and put the 2667 Mhz in and the About This Mac reported 64GB running at 2667MHz. The iMac was rock solid as I suspect it was running at the spec'd 2400Mhz even though it said 2667MHz. I also considered 128GB but after reading this thread (and I verified my BootCamp partition too) that 64GB is a hard stop limit for this 2017 iMac. That's fine. I don't really need 64GB, much less 128GB.
But what was not addressed as clearly in this thread as I hoped was the speed of the memory. If the 64GB is what is used and more than that is that "macOS shoves it into Wired Memory and Windows shoves it into the graphics memory", meaning 128GB (more than 64GB) is seen but not used, then could the same be true for RAM speed ? That is, if the specification is 2400MHz and some folks show the 2017 iMac using 2667MHz or 3200MHz DDR4, then could it also be that MacOS/i7-7700k "sees" whatever memory speed is spec'd by the DDR4 SODIMs but that in fact it ONLY runs at 2400MHz ?
My system clearly says in both the Windows 10 BootCamp partition and MacOS 64GB DDR4 2667MHz installed. But to be clear, I have not noticed or seen in any usage in Apps or Benchmarks any improvement, however slight with a bumped up RAM speed. I suspect the 2667MHz memory is reported as such but is clocked to 2400Mhz in real use. For that reason I did not bother to see about 3200MHz. My goal was quantity of memory more than speed anyway but I saw the 2667MHz deal and thought why not.
But the question remains. Aside from a hardtop 64GB cap which seems clear on this 2017 iMac, is the same true for SODIMM DDR4 speed ? How do I go about actually testing RAM speed usage? I'm more curious than needing an answer but if true, then while the total RAM cap might be a no-go above 64GB, if the speed is actually a thing of consequence, then perhaps it's worth finding faster RAM instead of more RAM on this iMac? Compatible DDR4 SODIMM RAM faster than 2400MHz does exist so technically it could be an upgrade ? Or is it just what we see, not what we notice in practice?
Any thoughts ?
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I tried doing speed tests between the 2400 and 2667 speeds. The difference simply in MHz isn’t that much. I think my numbers showed a small speed increase but the difference was within the variation of my tests. The 2667 seemed to be on the upper end where the 2400 seemed to be on the lower end. But there was a lot of overlap.
People on various sites said the difference between 2400 and 2667 on PC’s that could use the additional speed felt the speed bump wasn’t worth the upgrade.
Someone installed 3200 memory and was happy with the results. 2400 vs. 3200 would provide a better testing range.
People on various sites said the difference between 2400 and 2667 on PC’s that could use the additional speed felt the speed bump wasn’t worth the upgrade.
Someone installed 3200 memory and was happy with the results. 2400 vs. 3200 would provide a better testing range.