I’m looking to upgrade my iMac’s ram but don’t really know much about what’s compatible and what’s not. Is a ram with following features compatible with it?

Crucial 16GB DDR4 2400Mhz SODIMM CL17 DRx8 Ram (PC4-19200)

Thanks a lot.

  • Welcome to Ask Different :) What's the make and model of your iMac? – Nimesh Neema Sep 7 at 10:20
  • Thank you! :) it’s the latest model with 9th gen 3.7 ghz i5 processor, 8 gb ram, 2 tb fusion drive and Radeon Pro 580x GPU. – Dsenk Sep 7 at 10:37


You selected a DDR4-Generation module in the implementation of SO-DIM which is both matching.
But I am not quite sure about the frequency. DDR4 has two standard frequencies: 2400 and 2666 MHz. Normally 2400 is always supported as default, and the 2666 is optional for higher performance.
However Apple is saying you should use a 2666 MHz for the iMac Retina 5K 27-inch 2019 model.

So you should use a memory module that is a Unbuffered Nonparity DDR4 SDRAM 2666MHz (PC4-21333) SO-DIMM. The brand should not matter.

For detailed information what all that means take a look at wikipedia.


You selected a 2400 MHz module which normally should work, but apple seams to recommend 2666 MHz. To be 100% sure buy a 2666.


You selected a Crucial module, on their web site you can search for your system and list all memory modules that are compatible. Here you can only find 2666 MHz modules. So if you want to stick to crucial you can follow this link. That would be my suggestion because the modules match the Apple specificities and are also sold as compatible for your specific system.

Apple Information

On the web site you can view the specifications for the RAM modules.

Memory specifications (iMac Retina 5K, 27-inch, 2019)

This iMac model feature Synchronous Dynamic Random-Access Memory (SDRAM) slots near the bottom of the computer with these memory specifications:

Number of memory slots: 4
Base memory: 8GB (2 x 4GB DIMMs)
Maximum memory: 64GB (4 x 16GB DIMMs)

Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:


  • @Dsenk it looks like some people think my answer is resolving the question. If you also think so, please mark it as correct with the green arrow. – Felix Quehl Sep 10 at 20:22

Apple lists the iMac memory specifications at this page which will help you with a more general answer than just lots of yes/no questions.

Also, when shopping consider how helpful the seller is - most will want to be sure they sell you something appropriate instead of leaving you it figure out everything by dumping a mass of parts and hoping you can do the work to shop for fit.

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