A question about RAM

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A question about RAM

I know that RAM in an iMac needs to be installed in pairs, but for performance do the pairs need to be identical. I plan to buy a new iMac in the near future, and I'll be increasing the RAM using DIMMs from a 3rd party vendor. My question is which will give me the maximum performance?

• Replacing the 2 x 4 GB DIMMs that come with the iMac with 4 x 8 GB DIMMs (32 GB total)

• Replacing the 2 x 4 GB DIMMs that come with the iMac with 2 x 16 GB DIMMs (32 GB total), or

• Adding 2 x 16 GB DIMMs to the stock 2 x 4 GB DIMMs for a total of 40 GB?

Or does it make any difference other than, I would guess, 40 GB is better than 32 GB unless performance would deteriorate if the DIMM pairs are not identical.

Thanks in advance.

Posted on Jun 10, 2020 5:34 AM

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Answer 1

Top-ranking reply

Phil0124

Level 10

216,986 points

Jun 10, 2020 6:33 AM in response to Will Mardis

No, they do not have to installed in pairs, and no they do not have to be of the same size.

Yes, its recommended the RAM be installed in pairs for best performance ut it means pairs of the same speed and size of ram. Even then the performance difference is normally unnoticeable unless you do a lot of high demand tasks such as 3D rendering or 4K video editing, and even then its not a great big difference, and in almost all cases the extra RAM will overcome whatever performance difference there would be if you had the ram in pairs but less of it.

You can install a 16GB module and a 4GB module just fine or keep whatever is in the Mac and add other modules. So yes your combinations will work.

As BDAqua points out, the more RAM the better.

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Answer 2

BDAqua

Level 10

250,253 points

Jun 10, 2020 6:24 AM in response to Will Mardis

My vote is Adding 2 x 16 GB DIMMs to the stock 2 x 4 GB DIMMs for a total of 40 GB?

Matching RAM may indeed speed things up as far as benchmarks, but in my testing a 10% increase in RAM speed left a barely traceable <1% increase in overall speed, & extra RAM is almost always needed sooner or later.

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Answer 3

Will Mardis Author

Level 2

170 points

Jun 10, 2020 11:32 AM in response to den.thed

Thanks for the information. I plan to purchase the RAM from OWC. I've bought several items from them in the past and have always been satisfied with their pricing and quality. So, when I purchase my new iMac, I'll purchase 2 x 16 GB DIMMs from them for less than adding 8 GB to the iMac through the Apple Store. 40 GB ought to give me all the muscle I need.

I'm just waiting to see what Apple introduces at the upcoming WWDC. I don't want to purchase this year's model if the next has more whistles and bells. And don't they always!? But I'll need to do something soon; the HDD on my mid-2010 iMac is failing….

Again, thank you for your information.

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Answer 4

den.thed

Level 10

91,018 points

Jun 10, 2020 7:21 AM in response to Will Mardis

Yes adding 2 x 16 GB to the stock 2 x 4 GB for a total of 40 GB is a good move and will work just fine.

Also Mac's are picky and both the module spec's and compatibility are very important. Instead of guessing and trusting third party vendors at ebay or amazon, you should buy modules directly from suppliers like OWC macsales.com or Crucial.com that specialize in Mac RAM.

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A question about RAM

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