Memory upgrade compatibility list for iMac 2019-2020

[pldelisle]

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 number	Capacity	Amazon US	Amazon Canada	Amazon UK
CT8G4S266M	1 x 8 GB	Buy now	Buy now	Buy now
CT16G4S266M	1 x 16 GB	Buy now	Buy now	Buy now
CT32G4S266M	1 x 32 GB	N/A	Buy now	Buy now
CT2K8G4S266M	2 x 8 GB	Buy now	Buy now	Buy now
CT2K16G4S266M	2 x 16 GB	Buy Now	Buy now	Buy now
CT2K32G4S266M	2 x 32 GB	N/A	Buy now	Buy now

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

Compatible Crucial part numbers (Tested from Forum users):

Crucial CT2K32G4SFD8266 64GB Kit (32GB x2)


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

Part number	Capacity	Amazon US	Amazon Canada	Amazon UK
KCP426SS6/4	1 x 4 GB	Buy now	Buy now	Buy now
KCP426SS8/8	1 x 8 GB	Buy now	Buy now	Buy now
KCP426SS8/16	1 x 16 GB	N/A	N/A	N/A
KCP426SD8/16	1 x 16 GB	Buy now	Buy now	Buy now
KCP426SD8/32	1 x 32 GB	N/A	Buy now	Buy now

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

Part number	Capacity	Amazon US	Amazon Canada	Amazon UK
2666DDR4S08G	1 x 8 GB	Buy now	Buy now	N/A
2666DDR4S16G	1 x 16 GB	Buy now	Buy now	Buy now
2666DDR4S32G	1 x 32 GB	Buy now	Buy now	Buy now
2666DDR4S16P	2 x 8 GB	Buy now	Buy now	Buy now
2666DDR4S32S	4 x 8 GB	N/A	Buy now	Buy now
2666DDR4S32P	2 x 16 GB	N/A	Buy now	Buy now
2666DDR4S64S	4 x 16 GB	Buy now	Buy now	Buy now
2666DDR4S64P	2 x 32 GB	Buy now	Buy now	N/A
2666DR4S128S	4 x 32 GB	N/A	N/A	N/A

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

Part number	Capacity	Amazon US	Amazon Canada	Amazon UK
M471A5244CB0-CTD	1 x 4 GB	N/A	N/A	Buy now
M471A1K43CB1-CTD	1 x 8 GB	Buy now	Buy now	Buy now
M471A1K43DB1-CTD	1 x 8 GB	N/A	N/A	N/A
M471A2K43CB1-CTD	1 x 16 GB	Buy nowBuy now	N/A	Buy now
M471A2K43DB1-CTD	1 x 16 GB	N/A	N/A	N/A
M471A4G43MB1-CTD	1 x 32 GB	Buy now	Buy now	Buy now

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

• HMA81GS6CJR8N-VK *
• HMA851S6DJR6N-VK (original Apple RAM installed in 2020 iMac)

* 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

Rules of thumb :

1. Do not mix RAM modules with different capacity/speed/manufacturer. A OWC memory kit with Hynix ICs won't work with an OWC memory kit with Micron ICs, even if they are "For Mac", with the same speed, timings, comes from the same manufacturer, and other specs.
2. If you chose to upgrade to, for example, 2x32 GB, and have 2 memory slots free for future upgrade, chose Crucial RAM. It's the only RAM brand which has a unique ICs manufacturer which is Micron. Kingston usually have a locked BOM for ValueRAM Server RAM, but I can't find the same information for Mac RAM. Crucial is the only 100% certified compatible RAM and guarantee that it will work in the future when adding a second kit.
3. No experiment show that mixing Apple stock RAM with aftermarket RAM listed above is correctly operating at full speed and in dual channel. Don't mix Apple RAM with aftermarket RAM.
4. Memory must be installed in slot 1-3 and 2-4 when in kit of 2 SODIMM modules. If all 4 SODIMM are populated, make sure all ICs are coming from the same manufacturer. If not, dual channel is lost.

 

[noir_et_noir]

What about the Samsung M471A4G43MB1-CTD? 32GB stick? Specs all fall in line and have plenty of success history through here and Reddit especially back with the last Mac Mini release.
(Link: https://www.samsung.com/semiconductor/dram/module/M471A4G43MB1-CTD/)

Currently only $120 (at memory.net) for 32GB stick -- $480 if you want to max out to 128GB.


I feel like your warning of anything other than what's listed above unfairly rules out other viable producers including Samsung and Hynix RAM.

Edit: See it listed now ??

 

[pldelisle]

Certified Hynix RAM is hard to find. There are no tools to certify iMac compatibility even if we "know" it could work.

 

[Moshe1010]

What’s the difference between

• CT2K32G4S266M
• CT2K32G4SFD8266

 

[pldelisle]

What’s the difference between

• CT2K32G4S266M
• CT2K32G4SFD8266

The first is listed in Crucial Memory for Mac Systems, the second is not. But they share the same specs, voltage, timing, frequency, density, everything...

I think Crucial hasn't created a 64 GB kit yet specifically for the iMac 2020. They have the part listed in official documentation but the kit is still not listed for sale, probably because they want to have an iMac to test it. The CT2K32G4S266M will probably be on sale soon once Crucial got their hand on the iMac 2020.

 

[cadamwil]

Question, the processor in the top spec (standard proc) 27" iMac is an Intel® Core™ i7-10700K, correct? If so, why wouldn't it use DDR4-23400 (2933 Mhz) as listed in the processor specifications instead of the DDR4-21333 (2666 Mhz)? Isn't apple slowing it down a bit using sub top speed ram?

Install memory in your 27-inch iMac

Step-by-step instructions for replacing memory in the 27-inch iMac.

support.apple.com

Intel® Core™ i7-10700K Processor (16M Cache, up to 5.10 GHz) Product Specifications

Intel® Core™ i7-10700K Processor (16M Cache, up to 5.10 GHz) quick reference guide including specifications, features, pricing, compatibility, design documentation, ordering codes, spec codes and more.

ark.intel.com

 

[pldelisle]

Question, the processor in the top spec (standard proc) 27" iMac is an Intel® Core™ i7-10700K, correct? If so, why wouldn't it use DDR4-23400 (2933 Mhz) as listed in the processor specifications instead of the DDR4-21333 (2666 Mhz)? Isn't apple slowing it down a bit using sub top speed ram?

Install memory in your 27-inch iMac

Step-by-step instructions for replacing memory in the 27-inch iMac.

support.apple.com

Intel® Core™ i7-10700K Processor (16M Cache, up to 5.10 GHz) Product Specifications

Intel® Core™ i7-10700K Processor (16M Cache, up to 5.10 GHz) quick reference guide including specifications, features, pricing, compatibility, design documentation, ordering codes, spec codes and more.

ark.intel.com

Yeah the CPU support higher clock speeds. I don’t know why Apple is using 2666MHz on this 2020 iMac. When writing this post I followed Apple official specs. Someone will have to try faster RAM if it works but I doubt. BIOS will likely downclock the RAM to the supported 2666MHz.

 

[Moshe1010]

Question, the processor in the top spec (standard proc) 27" iMac is an Intel® Core™ i7-10700K, correct? If so, why wouldn't it use DDR4-23400 (2933 Mhz) as listed in the processor specifications instead of the DDR4-21333 (2666 Mhz)? Isn't apple slowing it down a bit using sub top speed ram?

Install memory in your 27-inch iMac

Step-by-step instructions for replacing memory in the 27-inch iMac.

support.apple.com

Intel® Core™ i7-10700K Processor (16M Cache, up to 5.10 GHz) Product Specifications

Intel® Core™ i7-10700K Processor (16M Cache, up to 5.10 GHz) quick reference guide including specifications, features, pricing, compatibility, design documentation, ordering codes, spec codes and more.

ark.intel.com

Probably due to heat. i7 and def. i9 are hot potatoes, especially in the outdated iMac infrastructure

 

[RyanXM]

I have 2666, 2933, and 3200 here and waiting for my 10-core build to arrive. I will be testing all three speeds to see if they will run at their max speed. All Kingston HyperX Gaming RAM. 128GB of each speed.

 

[KrazyKanuck]

(moved to a new thread)

 

[Fernandez21]

What are peoples thoughts on Samsung RAM? Looking at getting 2 of these for $250 for 64gb total while leaving the other 2 slots open for future upgrade to 128gb, or would it be ok to leave the 8gb from apple in there and have 72gb?

Samsung 32GB DDR4 2666MHz RAM Memory Module for Laptop Computers (260 Pin SODIMM, 1.2V) M471A4G43MB1

Samsung 32GB DDR4 2666MHZ PC4-21300 SODIMM M471A4G43MB1-CTD

www.amazon.com

 

[Fernandez21]

Or what about these Timetec ones? They look like the apple OEM ones with the black board, also $240 for 64gb.

https://www.amazon.com/dp/B084...cm_sw_r_cp_apa_i_w6lmFbX60N0FV

 

[CheesePuff]

I just purchased four of these, will let you know later this week how they perform on the 2020 i7:

Patriot Signature Series 8GB 2666MHz (PC4-21300) DDR4 SODIMM Memory Module

Patriot Memory's Signature Line DDR4 SODIMM memory delivers the quality, reliability and performance expected for today's notebook needs. This 8GB module is designed to run at 2666MHz (PC4-21300) at CAS 19 latency timings. Built using specific build-of-materials (BOMs) we ensure that every module...

www.amazon.com

 

[pldelisle]

Or what about these Timetec ones? They look like the apple OEM ones with the black board, also $240 for 64gb.

https://www.amazon.com/dp/B084...cm_sw_r_cp_apa_i_w6lmFbX60N0FV

I really don’t know this brand. I would stay with more known brands.

 

[pldelisle]

I just purchased four of these, will let you know later this week how they perform on the 2020 i7:

Patriot Signature Series 8GB 2666MHz (PC4-21300) DDR4 SODIMM Memory Module

Patriot Memory's Signature Line DDR4 SODIMM memory delivers the quality, reliability and performance expected for today's notebook needs. This 8GB module is designed to run at 2666MHz (PC4-21300) at CAS 19 latency timings. Built using specific build-of-materials (BOMs) we ensure that every module...

www.amazon.com

I didn’t even know they were still in business. Poor reliability back when I was building Pcs 7-8 years ago. Might have changed by now.

 

[pldelisle]

What are peoples thoughts on Samsung RAM? Looking at getting 2 of these for $250 for 64gb total while leaving the other 2 slots open for future upgrade to 128gb, or would it be ok to leave the 8gb from apple in there and have 72gb?

Samsung 32GB DDR4 2666MHz RAM Memory Module for Laptop Computers (260 Pin SODIMM, 1.2V) M471A4G43MB1

Samsung 32GB DDR4 2666MHZ PC4-21300 SODIMM M471A4G43MB1-CTD

www.amazon.com

As long as you get the modules listed in first post it’s fine.
Samsung makes memory more for OEMs and less for retail. That’s why almost nobody will have thoughts about Samsung, but it’s still a good memory brand. Good point of it is that they use their own DRAM chip, Samsung being a DRAM chip maker. So the whole module is Samsung made, just like Crucial which is Micron. Kingston is usually a mix of Hynix and Micron depending on which costs less when they order a batch of DRAM chips.

 

[CheesePuff]

I didn’t even know they were still in business. Poor reliability back when I was building Pcs 7-8 years ago. Might have changed by now.

They also make 'Mac' specific versions of their RAM like Crucial does, but the specs are identical, so going to try these. Worst case is I return them and pay $6 more per stick x4 for the Crucial brand.

 

[NewUsername]

Noob question. I wanted to order the Crucial memory, but I noticed a module of 16GB would cost me €70, whereas a 2x16GB kit would cost me €145. I suppose I should just order two separate models then and save €5? Or is there any difference between two separate 16GB modules and a kit of 2x16GB?

 

[pldelisle]

Noob question. I wanted to order the Crucial memory, but I noticed a module of 16GB would cost me €70, whereas a 2x16GB kit would cost me €145. I suppose I should just order two separate models then and save €5? Or is there any difference between two separate 16GB modules and a kit of 2x16GB?

Generally the RAM sold in kit is tested in kit. So both modules are "certified" to work perfectly together.

It's always better to buy as a kit.

 

[UbuntuFu]

Or what about these Timetec ones? They look like the apple OEM ones with the black board, also $240 for 64gb.

https://www.amazon.com/dp/B084...cm_sw_r_cp_apa_i_w6lmFbX60N0FV

I have Timetec memory in my 2011 Macbook Pro 15 inch. Has been working totally fine for 3 years now. Got this 2011 MBP for free and it had 4gb RAM so I upgraded it.

 

[NewUsername]

Generally the RAM sold in kit is tested in kit. So both modules are "certified" to work perfectly together.

It's always better to buy as a kit.

Yes, but in the case of Crucial even the model numbers are identical. So what I mean is: is there a difference between buying CT2K16G4S266M or between buying CT16G4S266M two times?

 

[pldelisle]

Yes, but in the case of Crucial even the model numbers are identical. So what I mean is: is there a difference between buying CT2K16G4S266M or between buying CT16G4S266M two times?

Re-read my post.

CT16G4S266M is a single module.
CT2K16G4S266M is a kit with 2x CT16G4S266M modules.

The CT2K16G4S266M is tested with 2x CT16G4S266M to perfectly work together. That's what I said.

For a 5$ difference, buy CT2K16G4S266M. Or even better, by 2x CT2K16G4S266M

 

[KrazyKanuck]

Yes, but in the case of Crucial even the model numbers are identical. So what I mean is: is there a difference between buying CT2K16G4S266M or between buying CT16G4S266M two times?

Well, I bought two pairs of the same Crucial 8GB two days apart from the same retailer and all four sticks are cooperating. But that is four "identical" sticks purchased in pairs over the space of two days.

 

[pldelisle]

Well, I bought two pairs of the same Crucial 8GB two days apart from the same retailer and all four sticks are cooperating. But that is four "identical" sticks purchased in pairs over the space of two days.

Yes it will work for sure at 99.999999999999%. They are just not "certified" together. This is the nuance.

 

[miretogo]

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).

As far as I can see, your source does not mention CL19 or 1.2V. Where do you have that from?