Crucial RAM 64GB Kit (2x32GB) DDR4 2666 MHz CL19 Memory for Mac CT2K32G4S266M

fast shipping, as described

I got a lot of problems with this computer since i installed those 2 sticks. Computer is frozing all the time and have to restart manually

It simply works with no problems.

After reading several accounts of installations, I moved one existing 4GB card to the third slot from the second where it had been, and put the two new 16GB cards into slots one and two. Fired my new 2017 27” iMac up and - presto! She booted up immediately.

Installed on my msi laptop without any problems. Now I got 32 gigs instead of 16. Was needed for video editing.

As always, Crucial is the best all around brand for Apples (upgradable) computers. Crucial is owned by Micron, a company that Apple themselves uses as an OEM supplier. If youve ever pulled RAM out of a Mac before, you might have seen Micron on the labels. Crucial supplies their own branded components that youd never see inside as OEM on a Mac, but the RAM itself is Micron underneath the Crucial label. Its the brand I always trust most with RAM upgrades on a Mac. Its not the cheapest, and is far from the most expensive. But it is the most dependable. And trust me, you want dependability if youre going to go through the hassle of upgrading the memory on a 2019 iMac.

After I had returned it as defective because it wouldnt work alongside my preinstalled RAM, I read a review (or a comment on a review, I cant remember which) stating that the key is to install the preinstalled RAM in slots 1-2 and this RAM in slots 3-4. In other words, instead of keeping the preinstalled RAM in slots 1 and 3 and adding this in slots 2 and 4, you must keep each of the the two different memory types together. I ordered it again and, sure enough, it worked the first time. This seems like such a critical piece of information that I wish Crucial would highlight it on the product page here on Amazon.

Unfortunately these did not work in my new 2019 iMac 27”. The Crucial website says they are compatible but they definitely didn’t work. I tried every configuration and nothing worked. My computer just wouldn’t boot with these installed....just a black screen.

It wasnt as easy as the 27, but an upgrade is possible for the 2017+ 21.5 iMac. It takes about 30-40m. MacSales has a great video that walks you through it step by step -- youll need to order the OWS repair kit. While you are at it, Id recommend changing out the old spinning hard-drive for a SATA SSD. Combined -- huge performance improvements from 8GB and stock Fusion (the PCIe will buffer your SATA SSD, so youll see a further gain). Note: in the 2017 iMac 21.5, the integrated microphone is three small holes is along the bottom right where the screen adhesive goes... make sure you leave those holes uncovered by adhesive -- just cut a little adhesive off around them.

Great price on Memory for my 27 iMac, and easy to install.