I am trying to upgrade my iMac 2019 5K 27' to 64GB.

Per Apple specs, the RAM should be PC4-21333, but the only one I seem to be able to find on Amazon or macsales.com seems to be PC4-21000.

Is there an actual difference, or is it just a rounding choice?

  • Is this about what kind of RAM you need, what kind of RAM Amazon has in stock, where to get PC4-21333 RAM, or something else. Please also have a look at help center, some of these possible questions are probably off-topic. – nohillside Jul 19 '19 at 6:07
  • reworded to make it clearer, thanks – meto Jul 19 '19 at 15:27
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    I've removed the secondary question as questions asking to recommend or find a Mac, book, tool, tutorial or other off-site resource are off-topic for Ask Different – grg Jul 19 '19 at 15:31

Crucial.com shows it being PC4-21300 so I would ignore Amazon.

See https://www.crucial.com/usa/en/compatible-upgrade-for/Apple/imac-%28retina-5k%2C-27-inch-3*0ghz-intel-core-i5%2C-2019%29#MEMORYFilters

  • in the link you provided it shows it being PC4-21000, unless I am mission something obvious – meto Jul 19 '19 at 6:29
  • From what I read its PC4-21300 DDR4 2666 – Thomas Nelson Jul 20 '19 at 4:13
  • Exactly. But I am looking for PC4-21333. Are you saying that PC4-21300 DDR4 2666 is indeed PC4-21333? – meto Jul 20 '19 at 18:02
  • forums.macrumors.com/threads/…. Apparently 21333 is something that apple has come up with. While 21300 is not the same it is compatible. It may be some time before the RAM manufacturers catch up with Apple. – Thomas Nelson Jul 20 '19 at 21:43
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    I looked on it, but there were no specs. in the system report only says DDR4 as type and 2667 MHz for speed – meto Jul 22 '19 at 3:52

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