RAM upgrade MHz difference

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Level 1

4 points

RAM upgrade MHz difference

Hello, I purchased a 27 inch 2017 iMac recently with standard RAM. I subsequently purchased 2 x 16 GB DDR4 RAM but only realized that the MHz was 2666 MHz. The Apple spec for my iMac is 2400Mhz. Can I still use them? Will it be ok to swap out the basic factory issues RAM (8 GIG) with the new 16 x 2 GIG for 32 GIG or even mix both RAMs for a grand total of 40 GIG RAM? Will it harm the computer if I do? Any advice is most appreciated as I haven’t even opened the new RAM yet just in case I need to resell it so I can get some partial refunding. Please help. Thank you very much in advance.

iMac with Retina 5K display, iOS 11.2.2

Posted on Jan 9, 2018 9:42 PM

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Answer 1

Top-ranking reply

Grant Bennet-Alder

Level 10

140,897 points

Jan 10, 2018 6:46 AM in response to Hamish Brown

Many Users have discovered that faster-speed rated MacBook Pro memory does NOT often work.

But it is worse than that. It ALMOST works, but can drive you crazy with infrequent but random crashes.

I strongly recommend you return it for an EXACT match is specs. Faster-speed rated RAM never runs any faster -- the memory timing is fixed inside the MacBook.

Nobody needs the trouble of stuff that almost works.

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Answer 2

JimmyCMPIT

Level 7

29,306 points

Jan 10, 2018 6:48 AM in response to Hamish Brown

With the information from Grant warning about using the correct RAM (which I 100% agree with) mixing and matching RAM even with the same latency, voltage speed and size can still introduce issues. This has gotten better over the years but it still can occur. Additionally only use RAM the specifically says it works with your model Mac. You may find less expensive RAM on sites that appear to be identical to what you need but unless the vendor has tested and verified with your model mac many of these products simply wont work.

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