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What Ram to order with the new 2019 IMac?

JuanitoIvanisios said:
Sorry, I had a typo in that long model description. The correct is CMSX64GX4M4A2666C18

This is the link to Amazon Germany: https://www.amazon.de/dp/B01BGZET9A/

I use Mactracker App to determine the spec of the Mac I want to upgrade and there they tell you about the actual RAM specs you will need to use. In fact I did upgrade my parents iMac 5K 2017 recently from 8GB to 32GB. There I used also Corsair RAM, but with 2400MHz to match the spec that was originally installed. The model is CMSX32GX4M2A2400C16 (https://www.amazon.de/dp/B01G26166W/). I would stick to the specs that are installed. If you pick 2666 it might not work at all, and if it works, it will run at the slower 2400.
Click to expand...

Thanks. I have heard from someone else here on the forum that the 2666 works fine in 2017 iMac. But, since I want to keep the original 8GB, would seem wise maybe to stick the same as that, 2400. Here's the link to the Corsair 2400MHz 32GB:
https://www.amazon.co.uk/dp/B01G26166W/

This is the right one? Anyone have any reason to say it's not the best choice?
It looks good, and is cheaper than Crucial:
https://www.amazon.co.uk/dp/B019FRCV9G/

  • Crucial 2400MHz - £149.57
  • Corsair 2400MHz - £142.47
 
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That is the Corsair RAM I have installed in the iMac 5K 2017 of my parents. The Corsair kit here is again CL16 vs. the CL17 from Crucial. So on paper it is a bit faster due to the lower latency. Warranty seems to be the same.

I did not keep the original 8GB in there though. I took the original RAM out and installed only the 2x 16GB modules. Looking at how Apple installs stock 2x 4GB they do skip an available slot. So just like with PC mainboards it seems like that there is dual channel utilized as well.

The stock configuration was:
1- empty
2- 4GB
3- empty
4- 4GB

For best performance on PC mainboards this is the same deal for dual channel setups. Although it should work, it is not recommended to install mismatched RAM modules as it will cause the loss of dual channel. Therefore when you use both RAM channels, the RAM module capacity should be the same for each RAM slot used. On PC there supposedly is a performance hit when you do not install matched capacities. I would assume that is the same with the iMac. If you really do need 40GB of RAM you should leave the 8GB sticks in the system as well. More RAM is still more RAM available to the system, which will be still faster as having to SWAP to the local disk.

I personally would take the 8GB out and replace them with 2x 16GB for a total of 32GB. If after that I do see in Activity Monitor that I need more, I would just pop in the 2x 4GB modules that were in there already. That is just my take though.
 
JuanitoIvanisios said:
Although it should work, it is not recommended to install mismatched RAM modules as it will cause the loss of dual channel.
Click to expand...
Really? Isn't that just for pairs? So just put the new pair in the empty 1 and 3 slots.

I would be very surprised if 32GB would work *better* than 40GB! But although that seems to be what you are saying and why you have done that, you also seem to believe the opposite, since you say:
JuanitoIvanisios said:
I personally would take the 8GB out and replace them with 2x 16GB for a total of 32GB. If after that I do see in Activity Monitor that I need more, I would just pop in the 2x 4GB modules that were in there already.
Click to expand...

Cool that the Corsair is working well though, thanks for that - think I'll be getting that then. But not removing my original 8GB!
 
128 GB RAM on the iMac i9

Only on the Radeon 580X Version possible or on the 575X too?

Thx
 
I just tried to install 16GB RAM in my iMac 2019 and it’s gone badly wrong.

The computer came with 8gb which has been working fine. I ordered 2 x 8gb crucial memory direct from Crucial. “
CT13492050 Crucial 16GB Kit (2 x 8GB) DDR4-2666 SODIMM” with the intention of upgrading to 24gb memory. I thought this would be the safest bet considering it came preinstalled with micron memory.

I inserted the new memory into the two empty slots, leaving the preinstalled memory alone, but the iMac would not turn on. I could hear the internal fans had kicked in, but the screen stayed black. There was no beep or anything to suggest an issue with the memory. I left the computer alone for several minutes before turning it off to diagnose the issue.

So I checked the memory was seated and noticed that slot 3 was a bit lose, so I pressed down on the memory to seat it and that seemed OK. Tried turning the computer on again but just a black screen again.

I checked again, and slot 3 still seemed not fully seated. It seems when I lever the memory back into the computer and then lever the memory back out again, slot 3 isnt fully seated again. Tried this a few times.

So I tried to remove the new memory, but I can’t even do that! The memory physically wont come back out of the machine. To test, I also tried removing the preinstalled memory (which I havent touched up until now) and I can’t even get that out of the machine either. It’s like all four memory modules are stuck and wont budge at all. I tried watching a video (again) of someone installing memory into an iMac 27in 2019 and in their case it took very little effort to take the memory out of the slot. It should in theory lift straight out.

What could I possibly be doing wrong?

I followed Apple’s instructions step by step and watched a video before starting the memory upgrade. I took my time and ensured the notch in the memory slot was positioned to the left before inserting it. I only attempted to insert or remove memory when the memory tray was hinged out of the machine as per instructions and video.

My local cellphone mast is down for maintenance so Apple’s attempts to ring me back failed. So in the meantime I thought I’d see what you guys can suggest?

I have a horrible feeling Apple will say this is not covered by the warranty and will put the blame on me. It’s a brand new iMac 27in!

Thanks, Ant

EDIT: Turns out I wasn't applying enough force when removing the memory. With the new memory taken out of the computer everything was back the way it was and working normally. I then tried removing the preinstalled memory and putting the new memory into those slots instead (seeing as I knew those slots were working), and the computer failed to start up. So I put all the memory back the way it was and this time inserted just one of the new memory into an empty bank - this time the computer started up and the new memory was recognised. So I took the new memory back out and swapped it for the other new memory and this time the computer failed to boot. So one of the new memory works and the other does not. It's going back to crucial. Frustrating but got there in the end.

As a side note to anyone else trying a memory upgrade, I managed to break a couple of the tiny retention springs in the memory cover door, so the door doesn't sit perfectly flush now. Really have to put the door back on with equal force in all four corners instead of trying to put one side in and hinge the other side (as I'd been used to with my MacBook Pro and other devices). Oops.
 
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FWIW I had a chat with Crucial (attached)

I asked about the 2x16gb kit -
CT2K16G4SFD8266 and they said no - but then they turned around and recommended what looks like exacrly the same part in single 1x16 RAM. DOH!

Their 1x16gb recommendation -
CT16G4SFD8266

Shopping that part online I found that buying Crucial direct was (in some cases significantly) less expensive than via resellers. They recommended Macsales - apparently a dealer of theirs - but $140 direct for 32gb vs $205. No thanks.
 

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tkodigital said:
Have any Canadians ever used Newegg for RAM? I found this, but would love to make sure I am buying the right RAM for the 2019 3.7ghz iMac. I am a noob to Mac!!!! https://www.newegg.ca/p/pl?d=CT2K16G4SFD8266+ I would rather get 2 32GB modules if anyone has a reccomendation
Click to expand...

I have never used them, but I did use Amazon.ca for that exact RAM. You really have to watch some sellers (same with amazon) due to the fact of where they are located, some do not include any duties or other fees. That could be costly and a time delay. I have heard good things of Newegg though.
 
I use the Crucial 2x 16GB:
Crucial CT2K16G4SFD8266 32GB (16GB x2) kit (DDR4, 2666 MT/s, PC4-21300, Dual Rank x8, SODIMM, 260-Pin)

The combination with the pre-installed 8GB (SK Hynix) works fine, with the right clock frequency (see screenshot).

iMac RAM.png
 
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I would like to have 16gb in my machine. If you aren't doing any serious music or video editing, is there any reason to go over 16gb? I wouldn't think so, but figured I would ask since the system can handle so much more.
 
KevinRightWing said:
I would like to have 16gb in my machine. If you aren't doing any serious music or video editing, is there any reason to go over 16gb? I wouldn't think so, but figured I would ask since the system can handle so much more.
Click to expand...

My new 2019 27" iMac has 16GB of RAM and that's probably enough for most people. For $19 shipped, I bought 2x4GB Sk Hynix sticks of RAM on eBay that someone removed from their 2019 iMac. Now, my iMac has 4x4GB of RAM.
 
I went to BH online and asked the Chat for 2X16GB Ram for my just ordered 2019 27" 3.7GHz 8GB Ram here is what they suggest:
Crucial 32GB DDR4 2400 MHz SO-DIMM Memory Module Kit for Mac (2 x16GB)
https://www.bhphotovideo.com/c/prod...4s24am_32gb_kit_16gb_x2.html/pageID/accessory

This is a different version than what I saw suggested in this thread several times:

Crucial 32GB DDR4 2666 MHz SODIMM Memory Module Kit (2 x 16GB)
https://www.bhphotovideo.com/c/product/1333839-REG/crucial_ct2k16g4sfd8266_32gb_kit_16gbx2_ddr4.html

Is this NOW the correct one to order (2400 MHz) instead of 2666 MHz?
 
HuskerHarley said:
I went to BH online and asked the Chat for 2X16GB Ram for my just ordered 2019 27" 3.7GHz 8GB Ram here is what they suggest:
Crucial 32GB DDR4 2400 MHz SO-DIMM Memory Module Kit for Mac (2 x16GB)
https://www.bhphotovideo.com/c/prod...4s24am_32gb_kit_16gb_x2.html/pageID/accessory

This is a different version than what I saw suggested in this thread several times:

Crucial 32GB DDR4 2666 MHz SODIMM Memory Module Kit (2 x 16GB)
https://www.bhphotovideo.com/c/product/1333839-REG/crucial_ct2k16g4sfd8266_32gb_kit_16gbx2_ddr4.html

Is this NOW the correct one to order (2400 MHz) instead of 2666 MHz?
Click to expand...

I can only say the ones I installed (once via Crucial direct, and the other pair via B&H) are working fine and they are exactly to spec at 2666 as per the RAM test. 2400 MHz will run at 2400 so IMO that's shortchanging yourself.

BTW - 2400 is the 2017 spec - so chances are you had an uneducated rep -
https://support.apple.com/en-us/HT201191#27inch2019
 
Apologies if this has already been covered, but what brand does Apple use for the iMac? The OCD part of me wants them to match.

Edit: Never mind, just saw it above, thanks.
 
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HuskerHarley said:
I went to BH online and asked the Chat for 2X16GB Ram for my just ordered 2019 27" 3.7GHz 8GB Ram here is what they suggest:
Crucial 32GB DDR4 2400 MHz SO-DIMM Memory Module Kit for Mac (2 x16GB)
https://www.bhphotovideo.com/c/prod...4s24am_32gb_kit_16gb_x2.html/pageID/accessory

This is a different version than what I saw suggested in this thread several times:

Crucial 32GB DDR4 2666 MHz SODIMM Memory Module Kit (2 x 16GB)
https://www.bhphotovideo.com/c/product/1333839-REG/crucial_ct2k16g4sfd8266_32gb_kit_16gbx2_ddr4.html

Is this NOW the correct one to order (2400 MHz) instead of 2666 MHz?
Click to expand...

Apple specs require a minimum of 2666 MHz RAM for any 2019 iMac. Do not use anything else that is slower.
 
ridgero said:
128 GB RAM on the iMac i9

Only on the Radeon 580X Version possible or on the 575X too?

Thx
Click to expand...

Actually, ALL 27" 2019 iMac can be upgraded to 128GB RAM (it is supported) with third party SODIMMS (not via Apple). Also the 21.5" iMacs could theoretically be upgraded to 64GB RAM (it is supported) but they are not designed to be upgraded by the user, as this could void the warranty, since the RAM is not user accessible.
 
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mrvo said:
saw that Crucial starts offering 3200 CL22 sticks (3200 CL22 is the Jedec spec for 3200MHz, anything exceeding them is programmed as XMP.)
CT2K16G4SFD832A - https://www.amazon.com/gp/product/B07Q7T9NSC/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

wonder if it works at full speed hmm..
Click to expand...

Would be nice to see results from using the 3200 MHz RAM. Theoretically, they should be compatible but to run at full speed, all RAM modules would have to be 3200 versions, otherwise they will be throttled to the lowest common denominator (i.e. 2666 MHz).

That said, at current prices, I do not believe that added benefit warrants the extra price.

Note that OWC performed earlier tests with 2400MHz RAM vs 2666 MHz RAM (a ~10% speed increase) in 2017 iMac but reportedly found only about a 2% improvement in overall speed, whereas going from 2666 to 3200 is a 20% increase.
 
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Hey
I Bought 2*16gb ram directly from OWC and After I installed them, I viewed the System Profiler, and it shows that the two Rams have the exactly same serial numbers..How come??
 

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Shiki29 said:
I Bought 2*16gb ram directly from OWC and After I installed them, I viewed the System Profiler, and it shows that the two Rams have the exactly same serial numbers..How come??
Click to expand...

Serial (and other) numbers are just strings returned by the RAM in response to specific queries. One of my OWC modules has Manufacturer: 0 and Part Number: Unknown. What you and I are seeing reflects, in my view, that OWC is packaging memory from wherever it can get it cheapest - there is no consistency apart from the OWC sticky label.
 
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