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Memory upgrade compatibility list for iMac 2019-2020

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The first post of this thread is a WikiPost and can be edited by anyone with the appropiate permissions. Your edits will be public.
@pldelisle thanks. Maybe you should add that to the wiki on the front page?

Is there any recommendation between brands (Kingston, OWC, Samsung)? or are they indistinguishable? Which one would you choose yourself in a new iMac 2020?

If I end up buying a 3200mhz RAM-module. Is there a proper way to test if it perform @ 3200mhz, and doesn't down clock to 2666mhz?
 
vjahbeas said:
Is there any recommendation between brands (Kingston, OWC, Samsung)? or are they indistinguishable? Which one would you choose yourself in a new iMac 2020?
Click to expand...
My order of preference :
1. Crucial
2. Kingston
3. Samsung
4. OWC

I would get Crucial if it was my money.
vjahbeas said:
If I end up buying a 3200mhz RAM-module. Is there a proper way to test if it perform @ 3200mhz, and doesn't down clock to 2666mhz?
Click to expand...
In System Report you can see the Current RAM speed.

This configuration is clearly not supported. It could introduce instability to the system. Very unlikely, but still. If you want more luck on your side, try 2933MHz. The Intel CPU natively support 2933 MHz : https://ark.intel.com/content/www/u...10910-processor-20m-cache-up-to-5-00-ghz.html
Make sure you can return the RAM easily if it doesn’t work...!

Crucial doesn't make 2933Mhz. That's why the iMac still comes with 2666MHz.
 
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anthony13 said:
Interesting, I wonder if micron ram will have the same compatibility issues with aftermarket ram?
Click to expand...
I would be very curious to experiment mixing micron stock ram with Crucial RAM for Mac. Theoretically it’s the exact same DRAM chips. Not the same PCB, but same chips. Micron must not produce a lot of different variants of DDR4 2666 MHz for Apple.
 
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pldelisle said:
I would be very curious to experiment mixing micron stock ram with Crucial RAM for Mac. Theoretically it’s the exact same DRAM chips. Not the same PCB, but same chips. Micron must not produce a lot of different variants of DDR4 2666 MHz for Apple.
Click to expand...
I just checked mine and it appears to also be micron. This will be a good experiment considering my stock 32gb dilemma that I now want to upgrade to 64. If I order 32GB of Crucial (2 16GB sticks), it might work without inhibiting dual channel and speed? If not I believe I can always return it.

1598293969337.jpeg
 
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My crucial ram should get here Wednesday or Thursday, I'll test it out with the stock micron ram and report back.
 
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anthony13 said:
My crucial ram should get here Wednesday or Thursday, I'll test it out with the stock micron ram and report back.
Click to expand...
This should be a very interesting test. You not only have the same manufacturer of ram chips, but the same size, too. Most people here have mixed sizes (unsuccessfully).
However, some have found just a later batch of the same 3rd party RAM can be not (fully) compatible.
 
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wilberforce said:
This should be a very interesting test. You not only have the same manufacturer of ram chips, but the same size, too. Most people here have mixed sizes (unsuccessfully).
However, some have found just a later batch of the same 3rd party RAM can be not (fully) compatible.
Click to expand...
The only case of this is OWC, which is not a DRAM manufacturer like Crucial or Samsung. If one batch were Micron and the other were Hynix, for sure it couldn’t work.
 
Soulflower said:
This is what I have of anyone is selling theirs. Thank you.
Click to expand...

This appears to be a single ranked chip. Majority of the kits here are dual ranked. I bought 2666 Mhz Single ranked Crucial Kit and it is running at 2666MHz, Although i did move the original 4GB modules to one channel and 16 GB modules to another one.

Now strictly speaking it will not give me dual channel but this is a Mac that highly optimizes power by aggressively slowing down CPUs when not in use. So i think having 40GB of memory gives me much better experience than have 32GB of real dual channel memory. ( Micro Benchmarks are synthetic and represent actual workloads ).
 
zen77 said:
Notice that 1RX16 - I think its a single ranked 4GB Module.
Click to expand...

Reading those signatures is well explained here.

This webiste also says:

"Generally Single Rank Memory is faster than Dual Rank Memory, in layman’s terms when a computer accesses Single Rank Memory it only has to go around the track once, where are Dual Rank it would have to go around the track twice."

"For the most part Dual Rank Memory can be used in conjunction with Single Rank Memory, and in some cases when using a large amount of memory such as 16GB, servers motherboards actually require you to use a mix of Single and Dual Rank Memory".


I think that I will just buy exactly same RAM (singe ranked) and try to put it in empty spots in order to get 16GB dual channel. It is the same RAM that is used in mac mini so there are lot of them to buy on aftermarket. I hope it will work...

EDIT:
According to MICRON website all MTA4ATF51264HZ-2G6 models are single ranked...
 
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Im giving up on crucial. Cant get a hold of it her.. In stock somewhere between 2 weeks - 3 months... Whats the next best option?
kingston KCP426SD8/32
samsung M471A4G43MB1-CTD

? dont want to lose any performance with dual mamba shamba stuff 🤦‍♀️ yeah, dont now s**t about ram, appreciate the help. 🙏
But I do know, now, that I should not use the stock ram. If so Im gonna do some test. But in the first place I would like 2X32gb, and having the possibility to upgrade with the same manufacture.

Maybe down side is thats its not sold as kit. one single
 
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zen77 said:
So i think having 40GB of memory gives me much better experience than have 32GB of real dual channel memory. ( Micro Benchmarks are synthetic and represent actual workloads ).
Click to expand...
Many benchmarks show you actually loose a lot of performance with your memory setup. Although these benchmarks are simply numbers, they are a very good indication of what’s going on. Sell back your 2x4GB apple stock RAM and get another 32 GB kit if needed. It will even be more stable.

4,8GB memory modules are single ranked. Anything above is dual ranked. Mixing and matching single with dual ranked isn’t good according to my experience.
 
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LadyNinja said:
Im giving up on crucial. Cant get a hold of it her.. In stock somewhere between 2 weeks - 3 months... Whats the next best option?
kingston KCP426SD8/32
samsung M471A4G43MB1-CTD

? dont want to lose any performance with dual mamba shamba stuff 🤦‍♀️ yeah, dont now s**t about ram, appreciate the help. 🙏
But I do know, now, that I should not use the stock ram. If so Im gonna do some test. But in the first place I would like 2X32gb, and having the possibility to upgrade with the same manufacture.

Maybe down side is thats its not sold as kit. one single
Click to expand...

Crucial is not in stock where you live ?

If not in stock then I would take Kingston RAM. Take 4 directly. While Kingston usually have the same BOM for a specific product, we never know in the future if newer modules will match the current ones that you have. Samsung is also very good. Many people reported that this kit works like a charm.
 
Hi All,

After reading as many posts regarding iMac 2020 ram upgrade as I can.
I would like to share my little finding here.

My mac is 3rd tier one. come with 2 x4gb Hynix ram.

1, I tested 2x16gb timetec kit. it works without mixing up with apple ram. once mix up with apple one. clock speed dropped to 2133mhz. ''Timetec Hynix IC Compatible with Apple 2019 iMac 27-inch w/Retina 5K Display, Late 2018 Mac Mini DDR4 2666MHz PC4-21300 2Rx8 CL19 1.2V SODIMM Memory R''
I then contacted timetec customer support. exchanged few emails, their agent said:
Hi xxx,
Thank you for letting us know!
Unfortunately, Apple has changed its memory configuration for this year's new iMac.
In order to activate the dual-channel mode and reach full speed, you would have to install all RAMs with the same capacity if you would like to occupy all RAM slots.

so if you want to mix timetec ram with apple ones, its a "NO GO"... but if you use timetec ram only, it works fine on 2020 iMac.

2, I then got hold of crucial 2x16gb kit too, "Crucial CT2K16G4S266M 32 GB Kit (16 GB x2) (DDR4, 2666 MT/s, PC4-21300, CL19, Dual Rank x8, SODIMM, 260-Pin) Memory for Mac"
its same finding, clock speed drops when mix up with apple ram. and run flawless without apple ram.
i have contacted 2 customer service agent from crucial. they kept saying that i should upgrade the bios of my iMac. as it lead nowhere with them. I went on apple.

3, I forgot to mention that I have tested mix up between 16gb x 2 crucial and 16gb x 2 timetec. totally 64gb. speed was also 2133mhz.

THE LATEST: I have a lengthy online chat with two apple agents, includes one senior agent. i am waiting for a call back and their senior CS will relay my call with an engineer and see if they can help to resolve this issue.
Once I have more information, i will be updating here.

UPDATE 1: I had to call apple back to chase up the call back and spoke with anther senior customer service agent. also we did more test, cleared NVRAM as apple suggested, installed ram as 16gb - 16gb -4gb -4gb. (16gb is crucial kits and 4gb is apple ram). as other youtuber suggested, it does show 2667mhz. but in reality, you do not benefit dual channel. as a result. you lose more than having 32gb@2667mhz. at the end, Apple agent was not sure why it happens like this, he was very helpful and will try to dig out more and come back to me. he also commented that it may not change the situation but he will try to find out more.

I will attach two screen shot, you will see the ram configuration and speed.
At the moment, mixing ram is a NO GO. unless Apple fixes this bar in its system..





pldelisle said:
Since many people were asking which RAM modules they could use to upgrade the 2019 or 2020 iMac, here are once and for all the compatible memory modules for both models. Feel free to add any kits you personally tested.



Memory upgrade compatibility list for iMac 2019-2020​


Compatible Crucial part numbers (compatibility verified and confirmed on manufacturer's website):

Part numberCapacityAmazon USAmazon CanadaAmazon UK
CT8G4S266M1 x 8 GBBuy nowBuy nowBuy now
CT16G4S266M1 x 16 GBBuy nowBuy nowBuy now
CT32G4S266M1 x 32 GBN/ABuy nowBuy now
CT2K8G4S266M2 x 8 GBBuy nowBuy nowBuy now
CT2K16G4S266M2 x 16 GBBuy NowBuy nowBuy now
CT2K32G4S266M2 x 32 GBN/ABuy nowBuy now

See the 2666 MT/s modules in Crucial Memory for Mac Systems


Compatible Kingston part numbers (compatibility verified and confirmed on manufacturer's website):

Part numberCapacityAmazon USAmazon CanadaAmazon UK
KCP426SS6/4 1 x 4 GBBuy nowBuy nowBuy now
KCP426SS8/8 1 x 8 GBBuy nowBuy nowBuy now
KCP426SS8/161 x 16 GBN/AN/AN/A
KCP426SD8/16 1 x 16 GBBuy nowBuy nowBuy now
KCP426SD8/321 x 32 GBN/ABuy nowBuy now


Compatible OWC part numbers (compatibility verified and confirmed on manufacturer's website):

Part numberCapacityAmazon USAmazon CanadaAmazon UK
2666DDR4S08G1 x 8 GBBuy nowBuy nowN/A
2666DDR4S16G1 x 16 GBBuy nowBuy nowBuy now
2666DDR4S32G1 x 32 GBBuy nowBuy nowBuy now
2666DDR4S16P2 x 8 GBBuy nowBuy nowBuy now
2666DDR4S32S4 x 8 GBN/ABuy nowBuy now
2666DDR4S32P2 x 16 GBN/ABuy nowBuy now
2666DDR4S64S4 x 16 GBBuy nowBuy nowBuy now
2666DDR4S64P2 x 32 GBBuy nowBuy nowN/A
2666DDR4S96S2 x 32 GB + 2 x 16 GBN/AN/AN/A
2666DR4S128S4 x 32 GBN/AN/AN/A


Compatible Samsung part numbers (compatibility cannot be verified on manufacturer's website):

Part numberCapacityAmazon USAmazon CanadaAmazon UK
M471A5244CB0-CTD1 x 4 GBN/AN/ABuy now
M471A1K43CB1-CTD1 x 8 GBBuy nowBuy nowBuy now
M471A1K43DB1-CTD1 x 8 GBN/AN/AN/A
M471A2K43CB1-CTD1 x 16 GBBuy now Buy nowN/ABuy now
M471A2K43DB1-CTD1 x 16 GBN/AN/AN/A
M471A4G43MB1-CTD1 x 32 GBBuy nowBuy nowBuy now


Compatible SK Hynix part numbers (compatibility cannot be verified on manufacturer's website):
* Not confirmed, but seems the only other model available on SK Hynix website. Shares same 1Gx64 or 2Gx64 organization spec as the original Apple RAM.

iMac 2019-2020 needs :
  • PC4-21333
  • Unbuffered
  • Nonparity
  • 260-pin DR (Dual Ranked) or SR (Single Ranked)
  • 2666MHz
  • CL19
  • 1.2v
  • Source : Install memory in an iMac.


See Installation instructions upon receiving your RAM module(s).

Please note that many people on this forum experienced problems when mixing genuine Apple RAM with third party RAM. It might not be possible to mix your genuine Apple RAM with the modules listed above without impacting stability and performance. Memory configuration with 2 or 4 memory modules coming from the same third party vendor is strongly recommended.

For troubleshooting RAM, please refer to this thread Memory upgrade troubleshooting in 2020 27-inch iMacs
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pldelisle said:
Crucial is not in stock where you live ?

If not in stock then I would take Kingston RAM. Take 4 directly. While Kingston usually have the same BOM for a specific product, we never know in the future if newer modules will match the current ones that you have. Samsung is also very good. Many people reported that this kit works like a charm.
Click to expand...

Thank you :) Really dont want to put the money out for 128gb right now. Do you think/know if the same problem could occur with the samsung?
 
Thank you Mister. Alot of helpful tips from you in this thread. I finally jumped on the Samsung. My experiense with Crucial was not all that im afraid. I love the fast support they offer. But when ive tried to purchase ram from them over several days, stating that my country where not in the shipping list, yet they keep telling me that they ship here. But not giving me any solutions...... Jesus just let me purchase in some way. Anyway. Happy to meet mr. Samsung.
 
LadyNinja said:
Thank you Mister. Alot of helpful tips from you in this thread. I finally jumped on the Samsung. My experiense with Crucial was not all that im afraid. I love the fast support they offer. But when ive tried to purchase ram from them over several days, stating that my country where not in the shipping list, yet they keep telling me that they ship here. But not giving me any solutions...... Jesus just let me purchase in some way. Anyway. Happy to meet mr. Samsung.
Click to expand...
Can't you order with Amazon ?
 
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