2019 iMac RAM 2400MHz

jonatious

macrumors member
Original poster
Sep 29, 2016
86
33
I purchased this following RAM
https://www.amazon.com/gp/product/B06XRBS4Y5
This RAM Is CL16 and I remember someone mentioning that the stock RAM is CL19. So is this discrepancy what causes the speed to go down to 2400MHz?

In that RAM someone has commented this
The memory works, and so part of me thinks it should get a higher star rating. It does not, however, work at the advertized 2666 Mhz transfer speed unless you are able to enable the XMP profile. My laptop's bios does not give any option for selecting the XMP profile, so the laptop will only run this memory at its default speed, which apparently is only 2400 MHz.

Is this something possible on iMac? Or my only option is to return this RAM and buy a CL19 RAM? Lower the latency should be better right?
 

Rockadile

macrumors 6502
Jun 11, 2012
467
188
I purchased this following RAM
https://www.amazon.com/gp/product/B06XRBS4Y5
This RAM Is CL16 and I remember someone mentioning that the stock RAM is CL19. So is this discrepancy what causes the speed to go down to 2400MHz?

In that RAM someone has commented this


Is this something possible on iMac? Or my only option is to return this RAM and buy a CL19 RAM? Lower the latency should be better right?
The RAM's base speed you purchased is 2400MHz with overclocking ability to 2666MHz. Since there's no XMP profile option in Mac, you have to return it.

This one should work at 2666MHz: https://www.amazon.com/Crucial-16GB...+sodimm&qid=1553736676&s=gateway&sr=8-1-spell
 

curmudgeonette

macrumors 6502a
Jan 28, 2016
559
430
California
The RAM's base speed you purchased is 2400MHz with overclocking ability to 2666MHz.

Looking through the Amazon page, buried in middle is the phrase: "Speeds start at 2400 MT/s." This is merely 2400 MHz (PC-19300) RAM that can be overclocked to 2666 MHz on systems where you can configure that in the BIOS.

Regarding the "16 clocks": To compare clock delays, they need to be compared at the same clock frequency. Increasing frequency requires increasing the clock delay. 16 clocks @ 2400MHz is about 18 clocks @ 2666MHz. Also, 19 clocks @ 2666 Mhz is about 17 clocks @ 2400 MHz.
 

jonatious

macrumors member
Original poster
Sep 29, 2016
86
33
Thanks guys, I did not realize that, I will order the Crucial one. Are there other options though? I can only see the Crucial one which has CL19 latency
 

Crispy Duck

macrumors regular
Nov 14, 2006
165
20
Manchester, UK

rugby4all

macrumors newbie
Mar 30, 2019
15
7
Not that expensive here in the US only 10-15% difference! At almost double the price I wouldn't recommend it but I had good experience in the past with OWC, hence being a repeat customer.
 

donkuok

macrumors newbie
Apr 14, 2019
14
5
Possible to remove the stock 8gb ram and check the RAM speed again? I believe the CAS Latency of ballistic one is CL17 and the stock one is CL19.
 

Kevbasscat

macrumors 6502
Oct 10, 2016
254
176
Banning, CA 92220
Well there is Corsair one with CL18 but some people seem to have problem while others don't on Mac.

https://www.amazon.com/CORSAIR-Veng...d=1554497514&s=gateway&sr=8-2#customerReviews

This is a typical example of how Corsair I believe a Micron/Crucial owner/manufacturer is misleading us like the other manufacturers and resellers. It is advertised as 2666MT/s, but without mentioning that it has the XMP2.0 "overclocking profile applied, yet is in fact saying "designed for high performance chips." These DDR4 that say high performance, are most likely really in your case, just 2400MT/s DDR4. Since Apple does not support INtel's XMP2.0 bios change that allows overclocking, we get the real lower clock speeds. Very misleading and confusing as well as they never admitted to having Intel's XMP2.0. profile applied. There should be some truth in advertising on Amazon, and I have had success in the past making Amazon aware of misleading labeling, and they required the vendor to correct it. I had purchased what was advertised as a DAC/headphone amp, when it was really just a headphone amp. The wording was misleading a and Amazon made them relabel it, and as a bonus the vendor let me keep that headphone amp and gave me a true DAC/headphone amp also for free. Sometimes it pays to gripe at. least to Amazon, as they tend to be on the consumer's side more than the vendors, because customer service and fast shipping is their advantage over others.
 
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Guy33

macrumors newbie
Sep 30, 2019
9
0

Kevbasscat

macrumors 6502
Oct 10, 2016
254
176
Banning, CA 92220
I bought these ones. When I put only them in the ram holder, I get 32gb of 2667mhz. But combined with the original Apple 8gb, it downgrades to 40gb 2400. Would you reccomend running on 32gb 2666 or go with the combined 40gb.?


I personally would go with 32Gb of 2666 MHz. I just don't care for mismatched anything in electronics, or my socks either, lol. The computer and the CPU were designed for 2666, why slow it down, since Apple has a tendency to under clock their CPU's anyway to help control cooling, although this may not be the case with your particular unit. Somehow to me, being a musician, I can't imagine things out of sync or slowed down by unmatched anything, but that's my personal opinion. Others may have differing opinions. I have 32 Gb in mine and the original 8Gb stored in a drawer in case I need to take it for service to Apple, but I learned that my ram is all compatible, so I'm putting the original back in for 40 Gb, since I just purchased the Proapps package from Apple, with Final Cut Pro x, Logic Pro x, Compressor 4, and Main Stage. More is better, right?:) Men...

Edit: I wrote a thread as an explanation to help with the confusion of the terms for ram and what the rules for publishing specs are to make it easier to understand. Maybe that can clear things up a bit. Their previous terminology was and to a degree still is.

2019 iMac ram Mismatched Or Underclocked to 2400MHz fix
 
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Guy33

macrumors newbie
Sep 30, 2019
9
0
I personally would go with 32Gb of 2666 MHz. I just don't care for mismatched anything in electronics, or my socks either, lol. The computer and the CPU were designed for 2666, why slow it down, since Apple has a tendency to under clock their CPU's anyway to help control cooling, although this may not be the case with your particular unit. Somehow to me, being a musician, I can't imagine things out of sync or slowed down by unmatched anything, but that's my personal opinion. Others may have differing opinions. I have 32 Gb in mine and the original 8Gb stored in a drawer in case I need to take it for service to Apple, but I learned that my ram is all compatible, so I'm putting the original back in for 40 Gb, since I just purchased the Proapps package from Apple, with Final Cut Pro x, Logic Pro x, Compressor 4, and Main Stage. More is better, right?:) Men...

Edit: I wrote a thread as an explanation to help with the confusion of the terms for ram and what the rules for publishing specs are to make it easier to understand. Maybe that can clear things up a bit. Their previous terminology was and to a degree still is.

2019 iMac ram Mismatched Or Underclocked to 2400MHz fix
Thank you very much for your answer!
I now got even bigger problems. I used only the Corsair modules and took the stock ones out and my iMac (2019 5k, not a week old) began crushing and crushing and crushing. When I tried to test the ram with the apple hardware test, no results found but with 3rd party software one programm told me faulty ram, the second one crashed immediately when trying to test the ram.

I'm sending the corsair back. Do you know which are the official Crucial RAM Models to get? Is it the CT2K16G4SFD8266?
 
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Kevbasscat

macrumors 6502
Oct 10, 2016
254
176
Banning, CA 92220
Thank you very much for your answer!
I now got even bigger problems. I used only the Corsair modules and took the stock ones out and my iMac (2019 5k, not a week old) began crushing and crushing and crushing. When I tried to test the ram with the apple hardware test, no results found but with 3rd party software one programm told me faulty ram, the second one crashed immediately when trying to test the ram.

I'm sending the corsair back. Do you know which are the official Crucial RAM Models to get? Is it the CT2K16G4SFD8266?


Yes I do, but Crucial is out on Amazon. You can get them from third party suppliers there though. Their warranty is the same.


The link says 16 Gb but you can choose 32 on that. page. Did you buy from Amazon?

Edit: I did not verify that this was listed as compatable with 2019 iMacs. My bad. I would buy OWC or Timetec, as they use Original apple ram suppliers.
 
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Guy33

macrumors newbie
Sep 30, 2019
9
0
Yes I do, but Crucial is out on Amazon. You can get them from third party suppliers there though. Their warranty is the same.


The link says 16 Gb but you can choose 32 on that. page. Did you buy from Amazon?
No I bought mine from an electronics shop. Going to return them tomorrow. I can get the Crucial here as well in an online shop (I'm from Switzerland). Thank you very much for your help! Appreciate it!
 

Guy33

macrumors newbie
Sep 30, 2019
9
0
Yes I do, but Crucial is out on Amazon. You can get them from third party suppliers there though. Their warranty is the same.


The link says 16 Gb but you can choose 32 on that. page. Did you buy from Amazon?

Edit: I did not verify that this was listed as compatable with 2019 iMacs. My bad. I would buy OWC or Timetec, as they use Original apple ram suppliers.
Would you still confirm, that these Curcial: https://www.alternate.ch/Crucial/SO-DIMM-32GB-DDR4-2666-Kit-Arbeitsspeicher/html/product/1399929 are the right ones to get - although they're not "officially" listed. Someone on this forum posted an answer from the producer and he confirmed they are caompatible, would you confirm that?
 

28Gauge

macrumors 6502a
Sep 4, 2011
620
343
DFW
Would you still confirm, that these Curcial: https://www.alternate.ch/Crucial/SO-DIMM-32GB-DDR4-2666-Kit-Arbeitsspeicher/html/product/1399929 are the right ones to get - although they're not "officially" listed. Someone on this forum posted an answer from the producer and he confirmed they are caompatible, would you confirm that?

I am running that exact RAM in my 2019 iMac i9 with no issues. Even though it is not listed as "official", it will work well. There are several forum members using it as well with great results.
 

Kevbasscat

macrumors 6502
Oct 10, 2016
254
176
Banning, CA 92220
Would you still confirm, that these Curcial: https://www.alternate.ch/Crucial/SO-DIMM-32GB-DDR4-2666-Kit-Arbeitsspeicher/html/product/1399929 are the right ones to get - although they're not "officially" listed. Someone on this forum posted an answer from the producer and he confirmed they are caompatible, would you confirm that?

I'm not sure tbh. The best way is to contact Crucial and ask them. For a while they were iffy about confirming, that's why I say that, just in case they have made up their mind yet or not. It's frustrating to be sure. There is another forum on this, I'll try to find it and link it here.
 

Guy33

macrumors newbie
Sep 30, 2019
9
0
I'm not sure tbh. The best way is to contact Crucial and ask them. For a while they were iffy about confirming, that's why I say that, just in case they have made up their mind yet or not. It's frustrating to be sure. There is another forum on this, I'll try to find it and link it here.
Thanks for your help. I already bought the RAM from Crucial and everything works fine, even at 2666mhz.
 

Kevbasscat

macrumors 6502
Oct 10, 2016
254
176
Banning, CA 92220
Wonderful news! Thanks for letting me know. Last time I checked Crucial was iffy on whether they would publish it as supported, for some reason. That's why I was unsure.
 
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