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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

macrumors 68000
Original poster
May 4, 2020
1,797
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Montreal, Quebec, Canada
Isn't the soldering the weak point in mfg? Over and over again, I see various threads about tossing devices/boards in the oven for 10 mins to 'fix' something
Do you have something against Mexico? 😂
[automerge]1602850559[/automerge]
where does it show CL19?
Can’t say for sure on this picture. But my guess is that it will fall back to JEDEC standard on CL19.
 
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warp9

Contributor
Jun 8, 2017
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483
I don't understand the point of this thread. I've never experienced nor heard of memory not working in an imac. I also don't see anybody here with any issues either.
 
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pldelisle

macrumors 68000
Original poster
May 4, 2020
1,797
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Montreal, Quebec, Canada
I don't understand the point of this thread. I've never experienced nor heard of memory not working in an imac. I also don't see anybody here with any issues either.
There were many threads starting at the launch of the iMac 2020 regarding wether or not memory modules were compatible or not. This thread was a summary of all certified modules and for people letting know to others that what they bought was working or not. iMac 2020 was fancy on which RAM work or not.
 
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warp9

Contributor
Jun 8, 2017
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483
There were many threads starting at the launch of the iMac 2020 regarding wether or not memory modules were compatible or not. This thread was a summary of all certified modules and for people letting know to others that what they bought was working or not. iMac 2020 was fancy on which RAM work or not.
Ok, but again nobody has claimed that some particular memory wasn't working. Just a lot of people asking the same question and discussing ram in general. I appreciate all the effort you went to but you would have been better off asking people to post ram that doesn't work. Of course, it would be pretty quite in here if you did that.

The imac needs DDR4 2666mhz SODIMM. That's the only requirement. Timings, voltages, etc. will all be within tolerance ranges. Doesn't matter the brand or capacity, as long as it's not defective (always test modules after installation).

Personally, I'm going with Nemix because they're almost half the price of the next cheapest brand.
 
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hoodafoo

macrumors regular
Oct 11, 2020
100
28
Lso Angeles
I don't understand the point of this thread. I've never experienced nor heard of memory not working in an imac. I also don't see anybody here with any issues either.

I've had issues with mac-specific ram made by 3rd parties in the past. Things might work great at first but then get wonky down a few months later. It'll even pass all diagnostics, but as soon as you slap in official apple ram, all problems go away
 
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hoodafoo

macrumors regular
Oct 11, 2020
100
28
Lso Angeles
The imac needs DDR4 2666mhz SODIMM. That's the only requirement. Timings, voltages, etc. will all be within tolerance ranges. Doesn't matter the brand or capacity, as long as it's not defective (always test modules after installation).

What do you use to test your ram?
 
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pldelisle

macrumors 68000
Original poster
May 4, 2020
1,797
1,221
Montreal, Quebec, Canada
Ok, but again nobody has claimed that some particular memory wasn't working. Just a lot of people asking the same question and discussing ram in general. I appreciate all the effort you went to but you would have been better off asking people to post ram that doesn't work. Of course, it would be pretty quite in here if you did that.

The imac needs DDR4 2666mhz SODIMM. That's the only requirement. Timings, voltages, etc. will all be within tolerance ranges. Doesn't matter the brand or capacity, as long as it's not defective (always test modules after installation).

Personally, I'm going with Nemix because they're almost half the price of the next cheapest brand.
I think you are a bit complaining for nothing. The goal was just to make clear what is certified compatible, what you should buy. Yes, people can post in here modules that doesn’t work, but the goal was exactly to avoid buying things that don’t work.

I personally find a computer of that price, especially an iMac, shouldn’t have such cheapo RAM. But that’s your money, not mine.
 
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Canaan_c

macrumors member
Jul 4, 2016
63
10
I installed Crucial CT2K32G4SFD8266 64GB Kit (32GB x2) on my 27" iMac 2020 at Slot 1,3 (Just replaced with the original rams)

The system said they runs at 2667Hz, but the Geekbench 5 report said it runs at 1333Hz....
It gave around 8500 Multi-core score (Mine is i7 8 core )

Is this normal? Are they running at dual channel?
 
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Canaan_c

macrumors member
Jul 4, 2016
63
10
I installed Crucial CT2K32G4SFD8266 64GB Kit (32GB x2) on my 27" iMac 2020 at Slot 1,3 (Just replaced with the original rams)

The system said they runs at 2667Hz, but the Geekbench 5 report said it runs at 1333Hz....
It gave around 8500 Multi-core score (Mine is i7 8 core )

Is this normal? Are they running at dual channel?

Here is my geekbench report
 
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Canaan_c

macrumors member
Jul 4, 2016
63
10
Hi AppleFans


iMac (Retina 5K, 27-inch, 2020)
3,8 GHz 8-Core Intel Core i7
AMD Radeon Pro 5500XT 8GB
Mac OS Catalina 10.15.6




I have tested 3 different sticks and this is the result :




CRUCIAL Total 32GB -- 2x 16GB Crucial CT16G4SFD8266 - DDR4 2666 1.2V CL19 - Geekbench 8890

CORSAIR
Total 64GB -- 4x 16GB Corsair CMSX32GX4M2A2666C18 - DDR4 2666 1.2V CL18 - Geekbench 9030

SAMSUNG
Total 32GB -- 1x 32GB Samsung M471A4G43MB1-CTD - DDR4 2666 1.2V CL19 - Geekbench 7730

SAMSUNG
Total 64GB -- 2x 32GB Samsung M471A4G43MB1-CTD - DDR4 2666 1.2V CL19 - Geekbench 8810



I have tested 32GB Crucial and 64GB Corsair and CRUCIAL is the winner ! and its between 32 and 64GB.




I hope this helps ;)

iMac (Retina 5K, 27-inch, 2020)
3,8 GHz 8-Core Intel Core i7
AMD Radeon Pro 5700XT 16GB
Mac OS Catalina 10.15.7

CRUCIAL
Total 64GB -- 2x 32GB Crucial CT32G4SFD8266 - DDR4 2666 1.2V CL19 - Geekbench 8450

WHY...
 
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pldelisle

macrumors 68000
Original poster
May 4, 2020
1,797
1,221
Montreal, Quebec, Canada
iMac (Retina 5K, 27-inch, 2020)
3,8 GHz 8-Core Intel Core i7
AMD Radeon Pro 5700XT 16GB
Mac OS Catalina 10.15.7

CRUCIAL
Total 64GB -- 2x 32GB Crucial CT32G4SFD8266 - DDR4 2666 1.2V CL19 - Geekbench 8450

WHY...
I don’t see any problem. Geekbench probably report the data rate, which is 1333 mhz. The double data rate (DDR) speed is 2666 mhz.
 
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Canaan_c

macrumors member
Jul 4, 2016
63
10
I don’t see any problem. Geekbench probably report the data rate, which is 1333 mhz. The double data rate (DDR) speed is 2666 mhz.
Thanks.

However how come my 64GB ram score is lower than whom have 32GB only?
 
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bananamax

macrumors newbie
Oct 20, 2020
1
0
Hi!

+1 searching differences between CRUCIAL CT2K32G4S266M and CT2K32G4SFD8266.
It looks like there are not so much differences...
Concretely, what are the risks of using the non-mac memories?
Is it possible to see some potential problems after months of use?
Are the geekbench tests totally the same?

Thanks for your precious help!
 
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pldelisle

macrumors 68000
Original poster
May 4, 2020
1,797
1,221
Montreal, Quebec, Canada
The only difference is in the materials used for building the PCB. One is lead free, which complies with Apple environmental policies. The other is not. The DRAM used is exactly the same. Both work fine in 2020 iMac.

Concretely, what are the risks of using the non-mac memories?
In this case, none.

Is it possible to see some potential problems after months of use?
Not with this one.

Are the geekbench tests totally the same?
Yes
 
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Ctoretto93

macrumors newbie
Oct 20, 2020
2
0
so are there any updates for the people that got the 32gb sticks of samsung ram and were getting shutdowns when trying to use 4 of them?

trying to get 64gb(2x32) right now and add more in the future so can't decide between the samsung or crucial.
 
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pldelisle

macrumors 68000
Original poster
May 4, 2020
1,797
1,221
Montreal, Quebec, Canada
so are there any updates for the people that got the 32gb sticks of samsung ram and were getting shutdowns when trying to use 4 of them?

trying to get 64gb(2x32) right now and add more in the future so can't decide between the samsung or crucial.
I'd personally say you are better with Crucial.
 
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warp9

Contributor
Jun 8, 2017
344
483
I want to add that CL19 (CAS latency) is not a requirement for imac memory. Most manufacturers use CL19 timings in their DDR4 2666mhz modules, except one: Kingston HyperX at CL15 for 16GB modules (CL16 for 32GB).

The performance difference depends on the application but you can expect at least +5% in games and even more in other usages like rendering or simulations. The Kingston ram is the same price as the other brands plus they test the fully assembled modules. Other manufacturers generally only test the raw chips before they go down the assembly line.

According to Amazon reviews, many people are successfully using them in their 2020 imacs. I plan to use them myself in a few weeks.

https://www.amazon.ca/dp/B08492TQGQ/
https://www.amazon.com/dp/B01N7K4DV4/
 
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no_fan_my_ass

macrumors newbie
Oct 20, 2020
10
0
I want to add that CL19 (CAS latency) is not a requirement for imac memory. Most manufacturers use CL19 timings in their DDR4 2666mhz modules, except one: Kingston HyperX at CL15 for 16GB modules (CL16 for 32GB).

The performance difference depends on the application but you can expect at least +5% in games and even more in other usages like rendering or simulations. The Kingston ram is the same price as the other brands plus they test the fully assembled modules. Other manufacturers generally only test the raw chips before they go down the assembly line.

According to Amazon reviews, many people are successfully using them in their 2020 imacs. I plan to use them myself in a few weeks.

https://www.amazon.ca/dp/B08492TQGQ/
https://www.amazon.com/dp/B01N7K4DV4/

I've read that the Kingston HyperX will run at CL19 in an iMac 2020 - have you seen otherwise?
 
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warp9

Contributor
Jun 8, 2017
344
483
I've read that the Kingston HyperX will run at CL19 in an iMac 2020 - have you seen otherwise?
I have not seen otherwise but that would be very bizarre if true. A memory controller will not modify the timings unless it's trying to keep them within voltage limits or bring all the modules down to the lowest common speed. Since the HyperX modules are designed to operate at CL15 at 1.2V at a 2666mhz frequency (per JEDEC spec), that's what you will get.

It sounds like someone mixed the HyperX modules with the stock modules, and it downclocked to the stock ram at CL19.

Anyways, I'm happy to test it and report back when the imac arrives.
 
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no_fan_my_ass

macrumors newbie
Oct 20, 2020
10
0
I have not seen otherwise but that would be very bizarre if true. A memory controller will not modify the timings unless it's trying to keep them within voltage limits or bring all the modules down to the lowest common speed. Since the HyperX modules are designed to operate at CL15 at 1.2V at a 2666mhz frequency (per JEDEC spec), that's what you will get.

It sounds like someone mixed the HyperX modules with the stock modules, and it downclocked to the stock ram at CL19.

Anyways, I'm happy to test it and report back when the imac arrives.

Thanks looking forward to your findings
 
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