Crucial16GB Single DDR4 2666 MT/s (PC4-21300) CL19 DR x8 SODIMM 260-Pin for Mac - CT16G4S266M

I have bought 8GBx 2 memory Rams, fixed them along with the Apple 4GBX2 Rams. The result is continious black screen..I have read online to change the arrangement. so I have tried all the below an I made sure its placed correctly1 & 3 Crucial // 2 & 4 OEM = BLack screen1 & 3 OEM // 2 & 4 Crucial = BLack screen1 & 2 OEM // 3 & 4 Crucial = BLack screen1 & 2 Crucial // 3 & 4 OEM = BLack screenMy iMAC 2017 18,3 3.4 GHz, only works with either ONLY crucial in 1- 3 or 2-4, or OEM in the same..I am so tired trying to get them all four to work.CAN SOMEONE PLEASE GIVE ME A SOLUTION....

Great product. As described and quick shipping

Sorry for my mistake, reviewed wrong product. Well be deleted soon.

Arrived with Prime fast, works perfectly as I used the Crucial UK website to identify the best modules to use and they provided a link to Amazon to buy the right ones.iMac 2019 27inch 5k Retina Model - existing base capacity 8GB; increased to 24GB.You can mix modules, you have to buy a kit or twin modules to fill in the two remaining slots.Gen. rule of thumb about RAM - buy in pairs and always fill in all available slots. 2 slots should remain free, never none or odd numbers i.e. 1/3.If you want to optimise you always put RAM with the highest capacity in the bottom (Bank 0) and 3rd (Bank 2) from the bottom. Then the original RAM modules swap to the new positions of slot 2 (Bank 1) and 4 (Bank 3).Where my pre-installed 2 NR 4GB modules were I swapped with the NEW 2 NR 8GB modules. And then put the already pre-installed 2 NR 4GB modules in the 2 remaining slots.

Having recently purchased one of the last 2020 27" iMacs from Amazon I thought it best to future-proof it as best I can, so purchased some additional RAM for it bearing in mind it only had 8GB, so purchased this Crucial CT2K16G4S266M 32 GB Kit which consists of 2 off 16GB DDR4 2666 Ram chips.Unlike the smaller 21.5" iMac and some of the newer models, the Ram in the 2020 27" iMac can be easily upgraded, and yes I can confirm that it's very easy to do and has resulted in the RAM going from a paltry 8GB to a far more impressive 40GB because the old RAM chips can be retained.Sure the new iMacs are coming out, but they seem to be missing ports on the back, and realistically I'm not going to be rendering 5K videos for the foreseeable future, mainly YouTube, emailing, and some photo editing, so have purchased Affinity photo editing software so am well sorted.This has to be one of the easiest fixes to speed up your computer and will future-proof it for many years. The Crucial RAM upgrade has to be one of the best buys at the moment, and aside from changing the HDD to SSD or using an external SSD to store your files on if you have a tiny internal SSD drive there aren't really a lot of other steps you can take to make your computer run faster.Highly recommended if you have a 2020 (or older) 27" iMac and want to speed it up a bit.

My 27" 5K Imac has the ability to upgrade/increase its Ram.I purchased a single 8gb stick and this I beleive is where I went wrong. I followed Apple's instructions and placed the stick in the bottom 4th slot, powered on and nothing, I then tried the 2nd slot and again nothing happened. Without the module installed my iMac rebooted.Turns out that despite what some reviewers have implied, you cannot mix 4gb x2 with an 8gb module. I have checked forums and have seen other users saying the same and also indicating that it could be that the iMac is being a bit fussy!Sadly I have returned my purchase for a refund, the only option now is to buy 2x4gb or 4x4gb or 2x 8gb or 1x16gb and replace the apple sodimm modules.

Bit of,a bargain at this price, (£125), bought to upgrade a recently purchased iMac.Went from 16 to 40Gb and notice a lot of difference. Start up times appear to have reduced and no slowing or spinning beach ball when having numerous windows open.I use proprietary structural engineering software running under windows 10 in a virtual environment (parallels) with native Mac AutoCAD, as well as MS office and a other bits and pieces.Since upgrading I can run a windows on one screen and a Mac screen without any loss of speed, brilliant.Excellent value and a brilliant, simple upgrade.

** 2019 27" 5k iMac**Firstly, this was put into the NEW 2019 iMac as above. I can confirm it works perfectly, no issues.PLEASE NOTE: I made a mistake in purchasing only one of these as I thought they came in pairs. That's my fault but they offer these in pairs slightly cheaper, but no big deal. They must be in pairs! I just didn't read it properly.Anyway, once I had both they are very easy to install (5 mins) and a reboot and you're off! I placed the new pair in the empty slots and left the original RAM from Apple (X2 4GB sticks) in the original slots they came in. So simple, and I now have 24GB RAM for less then £90. Speeds things up and will be future proof for some time now. Highly recommended.