2019 iMac seems low on memory

My 2019 iMac is struggling and I remember adding more RAM to a previous model. However, the answer to this similar enquiry How to increase my iMac's memory? - Apple Community seems to indicate that this isn't possible and I would be grateful for advice how I can improve it's performance please. I attach all the metrics requested in the enquiry above. Thanks in advance for any guidance.












[Edited by Moderator]

iMac 27″, macOS 15.3

Posted on Mar 9, 2025 5:41 AM

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Mar 9, 2025 7:49 AM in response to jaqui176

Yes, the RAM in your 27-inch iMac can be upgraded. Apple's guidance for that can be found here: Install memory in an iMac - Apple Support


To determine if a RAM upgrade is warranted, you can use the Memory Pressure info displayed by the Activity Monitor app while you use your computer. If the memory pressure graphic often displays in the red, then yes, a RAM increase may be helpful. If it usually displays in the green, then an upgrade is unlikely to be helpful.

Activity Monitor User Guide for Mac - Apple Support


As for the performance (speed) of your iMac, as @tbirdvet has posted an external Thunderbolt drive would speed things up.


If you'd like to learn more about what may be causing your iMac to "struggle", then please run an EtreCheck (free) evaluation of your Mac and post the generated report back here in a reply. EtreCheck is a safe and highly regarded utility application from a trusted developer and respected ASC contributor. The diagnostic report will not include any personal info. It simply gathers specifics about hardware performance and installed software that might be in conflict with the OS.


Please navigate to EtreCheck.com to download the utility. Be sure to Allow Full Disk Access when you install the app. Once you’ve run the app and created your report please post it with your reply to this message. 


Please note you must upload the full report. To see how, please clickHow to use Add Text when posting… EtreCheck Report.


We’ll use your EtreCheck report to look for the things that may be causing your problem and advise how to correct them.

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Mar 9, 2025 7:00 AM in response to jaqui176

You can add much more Ram to the 2019 27" iMac. I have the same model. Look at the rear behind the stand for a panel that is removable. I use Crucial memory sticks. You can check your Activity Monitor under memory to see how much is being used and what the swap is. You have a fusion drive so not as fast as a full SSD. I use an external Thunderbolt drive to boot from after I cloned my internal using Carbon Copy Cloner.

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Mar 17, 2025 3:55 AM in response to jaqui176

Swao Used (1.05 GB) seems high, as if your Mac was low on RAM at some point. However, there was plenty of available RAM (1.35 GB) for whatever workload you were running at the time you captured the EtreCheck report.


I would recommend keeping Activity Monitor open to the Memory tab while doing some of your regular stuff that is likely to consume RAM, to gather more information. A modest RAM upgrade may be helpful , and you have a 27” iMac that would make it easy. But I”m not sure one is necessary.

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Mar 17, 2025 4:06 AM in response to jaqui176

Your iMac has one of the 1 TB Fusion Drives where Apple really skimped on the amount of SSD storage - at a time when they should have been including more of it.


The original 1 TB Fusion Drives has 128 GB of SSD space, but yours has only 32 GB (Wikipedia) or maybe only 28 GB (EtreCheck). Fast storage, but not nearly enough of it.


Fortunately, your Mac has USB-C / Thunderbolt ports that can support USB 3.1 Gen 2 / NVMe or Thunderbolt 3 / NVMe SSDs. Even a USB-A (USB 3.0) / SATA SSD might be an overkill improvement over the Fusion Drive. But the USB 3.1 Gen 2 / NVMe ones are faster and not much more expensive.


I’d think an external startup SSD would help, though there may also be issues with your software installations that could use attention.

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Mar 20, 2025 1:26 PM in response to jaqui176

You only provided the DriveDx report for the SSD, we also need the DriveDx report for the internal Hard Drive as well.


I'll need to review the EtreCheck a bit later when I have more time unless another more knowledgeable contributor wishes to chime in since I am not a macOS software expert.

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Mar 21, 2025 8:25 AM in response to jaqui176

I don't see any issues with either internal drive, so I'm not sure what the write speed is slow slow. Of course the internal hard drive could have some sort of problem that is not reflected in the health information (rare but it does happen).


If you haven't done so already, I would run Disk Utility First Aid on the Fusion Drive and the hidden APFS Container. Even if the First Aid summary says everything is "Ok", click "Show Details" and scroll back through the report to see if any unfixed errors exist. If there are errors, then run First Aid again until the errors are gone. If after a couple of scans the errors remain, then you will need to run First Aid while booted into Recovery Mode.


You can try installing macOS onto an external USB3 SSD to compare results.

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Mar 21, 2025 7:26 PM in response to jaqui176

That SSD is fine.


However, I would not use the memory in the Amazon link even though it is Crucial memory. Nowhere in the product documentation does it say "Mac Compatible" or "For Mac" which is a real red warning flag for me. These days you cannot purchase memory for any system based solely on memory speed. There are many more memory timings that Apple does not reveal which must match for compatibility. If you get a Crucial part number for a memory module that is guaranteed compatible with your specific Mac and that part number is on the product page of a third party reseller, then it should Ok, but you will need to verify the memory you receive has that same exact part number. Crucial will list "For Mac" or "Mac Compatible" on the plastic packaging the memory is packaged (at least it still did the last time I purchased memory for a Mac several years ago). It can be difficult confirming the part number on a third part seller's page is the same as what Crucial lists as compatible (Crucial tends to have two part numbers, and some numbers are mostly the same except for some small differences).


FYI, it seems Crucial currently has no compatible memory for your iMac at least in the US...see this link:

https://www.crucial.com/compatible-upgrade-for/apple/imac-(retina-5k--27-inch--2019)-imac-19-1?_gl=1*163g652*_up*MQ..*_ga*MTIyMzI1OTI3Ny4xNzQyNjEwMDg5*_ga_6H4RYWV7QY*MTc0MjYxMDA4OC4xLjEuMTc0MjYxMDEzNy4wLjAuMjA2MTE5MjA5MQ..


I know that Crucial has no memory for much older Macs, but surprised/disappointed they don't have memory for a 2019 model. I know another respected forum contributor mentioned the other day that Crucial no longer sells memory for Macs.



Another option is to purchase memory from OWC. OWC has official resellers in other regions.


https://www.owc.com/partners/where-to-buy/

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Mar 20, 2025 11:33 AM in response to HWTech

Drive DX seems to suggest physical state OK (with slightly elevated temperature)?

So, I'm about to order some new RAM, but also curious how I should go about solving the identified minor issues if someone's able to point me to a tutorial (YouTube only had one on how to generate the report)?


Once the RAM is installed and if it helps, I will look into a new start-up drive.

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Mar 17, 2025 1:30 AM in response to D.I. Johnson

Thank you both so much for your help and clear instructions. I have run the EntreCheck and happily there are no major issues. Plenty of minor issues though, so I would be grateful for any pointers as to which of these I should adress as a priority & hopefully speed-up its performance. I have attached the report as extra text.


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Mar 21, 2025 10:09 AM in response to jaqui176

Thanks HWTech - can confirm there were no errors showing on either the Fusion drive or hidden APFS container. I also spent ages How to fix a split Fusion Drive - Apple Support doing this process this afternoon in case the fusion drive had split (which hasn't improved performance, so I guess it hadn't!)


So, from all the guidance I have received, it would seem that a new SSD drive to act as start-up disk would be useful, along with a RAM upgrade. I would be grateful if you experts wouldn't mind checking whether the ones I have chosen are suitable, and if not or there are better or cheaper options, please suggest alternatives (with a link if possible) as this has been quite a steep learning curve and I don't want to waste time / money pursuing refunds if I've missed something critical!


https://amzn.eu/d/b5Jofnb RAM


https://amzn.eu/d/cPbVL2K Thunderbolt 3 NVMe SSD


Thanks so much in advance

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Mar 17, 2025 1:50 AM in response to jaqui176

I haven't upgraded the RAM yet as the memory pressure is green and based on what you've explained above, it may not be the issue. Think it makes sense to await analysis of the EC report. New start-up drive option is also possible - appropriate tutorials sourced. Would welcome recommendations for a suitable drive for this if anyone has the time to share one or two please. Many thanks in advance.

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2019 iMac seems low on memory

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