55 of 55 people found the following review helpful  Take some deep breaths, stay calm and don't give up...these will work in the 27" iMac (2017), August 26, 2017 By Amazon Groupie (Southern OR) This review is from: Crucial 32GB Kit (16GBx2) DDR4 2400 MT/s (PC4-19200) DR x8 SODIMM 260-Pin for Mac - CT2K16G4S24AM (Personal Computers) Whoo hoo! Just successfully installed these in a new 2017 iMac after four tries. Nothing like a black screen on an expensive new device to cause stomach upset and borderline freaking out. My process went like this...open Apple documentation online. Read up on installing memory. Open Amazon reviews for memory just purchased, reread questions and first page of reviews. Decide to move Apple memory to other slots when installing. Unplug powered off iMac and remove network cable (hey, I figure better safe than sorry, I even turned off the keyboard and mouse, lol!). Use small screw driver to push in the memory bay door release switch. You have to push further in than you would expect. Bay door pops up on on end, remove door by pulling out and off. It's tight and makes a little bit of metal grating on metal sound. Press the two levers outwards, pull towards you and the memory bay drops down. Apple memory is in the bottom and middle slot. i removed laid down exactly as... Read more
28 of 29 people found the following review helpful  Black Screen? Try moving the modules, August 9, 2017 This review is from: Crucial 32GB Kit (16GBx2) DDR4 2400 MT/s (PC4-19200) DR x8 SODIMM 260-Pin for Mac - CT2K16G4S24AM (Personal Computers) Got a black screen like I did? Try moving the memory around in different combinations while restarting in between. I did finally manage to get the 32GB Crucial Memory to work with the 8GB Apple Memory for a total of 40GB, but it took some experimentation. My 2017 27" iMac with 8GB of memory came with two 4GB modules installed in slots 2 and 4. First, I installed the Crucial memory in slots 1 and 3 and got nothing but black screen. Pulled everything out and reseated with the same black screen. Removing the 8GB of Apple memory worked, but left me with only 32 in slots 2+4. Reinstalling the Apple memory in slots 1+3 put me back to a black screen. Following that I moved the Apple memory to slots 1+2 and the Crucial to 3+4. This worked! 40GB total memory. However, the memory is mismatched so there's a massive performance hit in this configuration. At this point, I shut down and tried the first configuration one last time--Apple memory in 2+4 and Crucial... Read more
16 of 16 people found the following review helpful UPDATE: IS comparable with original Hynix single rank 8GB memory that comes installed in a 2017 27" 4.2 GHz i7 iMac., September 27, 2017 By RONALD D. FERRELL (NASHVILLE, TN United States) This review is from: Crucial 32GB Kit (16GBx2) DDR4 2400 MT/s (PC4-19200) DR x8 SODIMM 260-Pin for Mac - CT2K16G4S24AM (Personal Computers) UPDATE: Changing my rating from 2 to 5 stars. This memory IS comparable with the 8GB Hynix Mac memory. You have to fully remove the original memory, install this kit in the first two rows and then install the original Mac memory in the last two rows. Installing the chip in an alternating pattern like the original memory is installed will not work. Hope that helps!
This memory works by itself in my two new 2017 27" 4.2 GHz i7 iMacs, but not with the original 8GB Hynix Mac memory and vice versa. I called Crucial and it is an issue with the new iMac not liking the mix of single rank and dual rank memory. If you purchase, just know you might have to remove your base memory to get this to work if your base memory is single rank memory.
Attached is a photo of the original mac memory that this crucial memory IS NOT comparable with.
Buyer beware. | 
