Memory upgrade troubleshooting in 2020 27-inch iMacs

[JED POLAND]

I ordered a stick of the same part number as already installed.
Let's see how it works out - most likely I will be able to tell in less than 24 hours.

 

[dizmonk]

Okay I'm so confused... I had 24gb (the original 8gb from Apple and then another 16gb from V-color/amazon). I kinda got the point about the whole dual channel thing so I went and bought 2 pair of identical 16gb Kuesney/amazon for 64gb. This is what I've got. It went down to 2400Mhz. What the hell am I doing wrong?

 

[JED POLAND]

Pretty strange!
What I see on mine:
"Your Mac contains 4 memory slots, each of which accepts
a 2667 MHz DDR4 memory module."

Could it be that you bought 2400 MHz modules instead of 2666?

 

[dizmonk]

Pretty strange!
What I see on mine:
"Your Mac contains 4 memory slots, each of which accepts
a 2667 MHz DDR4 memory module."

Could it be that you bought 2400 MHz modules instead of 2666?

 

[dizmonk]

I don't think so.....

 

[JED POLAND]

All seems OK...let the smarter people chime in.

 

[wilberforce]

I don't think so.....

What MHz does it report if you just put two of the sticks in? (Say in slots 2 and 4).
If it still gives 2400 MHz, I think you may actually have 2400 MHz sticks despite the description on Amazon. Or there is some incompatibility.
Do you have a photo of the label on the stick?
Also a screenshot of the "Memory" under "System Report" under "About This Mac"

 

[JED POLAND]

So I installed second 32 GB stick this morning and generally, all seems fine.

For a better overview, Novabench:

40 GB (8+32)
Score: 2957
CPU: 1570
GPU: 911
Disk: 181
RAM: 295 @17978 MB/s

Geekbench 5: 1245/7310

32 GB
Score: 2994 (!)
CPU: 1612 (!)
GPU: 915
Disk: 186
RAM: 281 @17841 MB/s

Geekbench 5: 1322/7071

64 GB (32+32)
Score: 3109
CPU: 1629
GPU: 954
Disk: 168
RAM: 358 @27923 MB/s

Geekbench 5: 1383/8848


Other than sudden drop in SSD performance (why???) I am happy camper.
What's interesting here, the GPU seems to have gotten some room to breathe

 

[wilberforce]

So I installed second 32 GB stick this morning and generally, all seems fine.

For a better overview, Novabench:

40 GB (8+32)
Score: 2957
CPU: 1570
GPU: 911
Disk: 181
RAM: 295 @17978 MB/s

Geekbench 5: 1245/7310

32 GB
Score: 2994 (!)
CPU: 1612 (!)
GPU: 915
Disk: 186
RAM: 281 @17841 MB/s

Geekbench 5: 1322/7071

64 GB (32+32)
Score: 3109
CPU: 1629
GPU: 954
Disk: 168
RAM: 358 @27923 MB/s

Geekbench 5: 1383/8848


Other than sudden drop in SSD performance (why???) I am happy camper.
What's interesting here, the GPU seems to have gotten some room to breathe

Novabench GPU and Disk scores are not reliable/meaningful, ignore them. Use Geekbench 5 Compute for GPU, and Blackmagic for disk tests.
Good to see your 2x32GB seems to be running as it should

 

[Nemanja604]

The Geekbench results were 1245/7310 but what got me was the speed: 1333 Mhz, although I presumed it was OK due the way it is measured (correction needed).

Anyone knows what is 1333 Mhz Geekbench about? I got the same result with same specs.

 

[wilberforce]

Anyone knows what is 1333 Mhz Geekbench about? I got the same result with same specs.

Bus frequency 1333 MHz times DDR (Double Data Rate) gives 2667 MHz data rate.

However I believe Geekbench is just reporting the type of RAM (i.e., 1333 MHz frequency DDR RAM), and not the actual frequency it is running at.

 

[mikehalloran]

Other than sudden drop in SSD performance (why???)

Always run that test twice and believe the second result. Often, the first test on an SSD will give terrible results and a second one done immediately after will be correct. If both tests are equally bad, there's a problem but, with new hardware, it can sometimes be the test.

Google is your friend.

 

[JED POLAND]

I did it multiple times.

 

[dizmonk]

What MHz does it report if you just put two of the sticks in? (Say in slots 2 and 4).
If it still gives 2400 MHz, I think you may actually have 2400 MHz sticks despite the description on Amazon. Or there is some incompatibility.
Do you have a photo of the label on the stick?
Also a screenshot of the "Memory" under "System Report" under "About This Mac"

Well, you were right. Someone at this company screwed up. Sticks say 2666 but when installed are 2400. Guess it's time to ship it back to Amazon. Is this common? Thanks for the suggestions. I'm not sure I'm going to stick with 64gb anyway. Is there a significant performance difference between 24gb, 32gb or 64gb configured properly?

 

[JED POLAND]

I suggested 2400 even before Wilberforce .

32 GB seems to more than enough and best bang for the buck.

 

[dizmonk]

I suggested 2400 even before Wilberforce .

32 GB seems to more than enough and best bang for the buck.

Thanks.. Missed that one. Appreciate it.

 

[JED POLAND]

Check on YT (Max Tech?) - he greatly explains and proves with the numbers, the amount of the memory needed.

 

[wilberforce]

Well, you were right. Someone at this company screwed up. Sticks say 2666 but when installed are 2400. Guess it's time to ship it back to Amazon. Is this common? Thanks for the suggestions. I'm not sure I'm going to stick with 64gb anyway. Is there a significant performance difference between 24gb, 32gb or 64gb configured properly?

32GB is plenty for most people. 64GB or more is usually needed for those with special needs, such as lots of video editing, want to have hundreds of Chrome tabs open, virtualization, etc. Getting 2x16GB leaves the option open of adding another 2x16GB in the future.
I agree, Max Tech does a pretty good job showing what you gain from different amounts of RAM.
Kuesuny is not a brand I am familiar with.
Crucial has the best reputation, but also is a bit more expensive.
I also tested Timetec and found no discernible difference between it and Crucial.
Others swear by OWC, but there have been reports of kernel panics on 2020 iMac using OWC RAM, but this may be just unfair coincidence.

Crucial 32GB Kit (16GBx2) DDR4 2666 MT/s (PC4-21300) CL19 DR x8 SODIMM 260-Pin for Mac - CT2K16G4S266M

CT2K16G4S266M is a 32GB Kit consisting of (2) 16GB Dual Ranked DDR4 SODIMM modules that operates at speeds up to 2666 MT/s and has a CL19 latency. It is an Unbuffered SODIMM. It conforms to the industry standard DDR4 SODIMM layout of 260 pins and is compatible with systems that take DDR4 2666MT/s...

www.amazon.com

Timetec 32GB KIT(2x16GB) Compatible for Apple DDR4 2666MHz / 2667MHz for Mid 2020 iMac (20,1/20,2) / Mid 2019 iMac (19,1) 27-inch w/Retina 5K, Late 2018 Mac Mini (8,1) PC4-21333 /PC4-21300 MAC RAM

Timetec – Memory of a lifetime Compatible with (But not Limited to): *Please click image for more compatible systems model Need to know if this part is compatible? Contact us with manufacturer and model information of your motherboard

www.amazon.com

 

[JED POLAND]

Novabench GPU and Disk scores are not reliable/meaningful, ignore them. Use Geekbench 5 Compute for GPU, and Blackmagic for disk tests.
Good to see your 2x32GB seems to be running as it should

2400 MB/s write/read. Not bad, I think.

 

[MauriceG]

32GB is plenty for most people. 64GB or more is usually needed for those with special needs, such as lots of video editing, want to have hundreds of Chrome tabs open, virtualization, etc. Getting 2x16GB leaves the option open of adding another 2x16GB in the future.
I agree, Max Tech does a pretty good job showing what you gain from different amounts of RAM.
Kuesuny is not a brand I am familiar with.
Crucial has the best reputation, but also is a bit more expensive.
I also tested Timetec and found no discernible difference between it and Crucial.
Others swear by OWC, but there have been reports of kernel panics on 2020 iMac using OWC RAM, but this may be just unfair coincidence.

Crucial 32GB Kit (16GBx2) DDR4 2666 MT/s (PC4-21300) CL19 DR x8 SODIMM 260-Pin for Mac - CT2K16G4S266M

CT2K16G4S266M is a 32GB Kit consisting of (2) 16GB Dual Ranked DDR4 SODIMM modules that operates at speeds up to 2666 MT/s and has a CL19 latency. It is an Unbuffered SODIMM. It conforms to the industry standard DDR4 SODIMM layout of 260 pins and is compatible with systems that take DDR4 2666MT/s...

www.amazon.com

Timetec 32GB KIT(2x16GB) Compatible for Apple DDR4 2666MHz / 2667MHz for Mid 2020 iMac (20,1/20,2) / Mid 2019 iMac (19,1) 27-inch w/Retina 5K, Late 2018 Mac Mini (8,1) PC4-21333 /PC4-21300 MAC RAM

Timetec – Memory of a lifetime Compatible with (But not Limited to): *Please click image for more compatible systems model Need to know if this part is compatible? Contact us with manufacturer and model information of your motherboard

www.amazon.com

I have good experiences with Timetec. Upgraded 4 iMacs. They are all still running fine. In Europe these modules are cheaper than Crucial. I have read some horror stories about OWC, but their aftersales seems to be very good.

 

[Bigyid]

Hi Guys,

Ive just bought 2 x 8gb CRUCIAL RAM

CT8G4SFRA266​

Ive read through thread and just wanted to know if the above ram is suitable for the iMac 5k 2020 and will running it with stock 2 x 4gb apple ram be okay until I get another two crucial ram to match? or should I just ditch the apple ram for now?

 

[pldelisle]

Hi Guys,

Ive just bought 2 x 8gb CRUCIAL RAM

CT8G4SFRA266​

Ive read through thread and just wanted to know if the above ram is suitable for the iMac 5k 2020 and will running it with stock 2 x 4gb apple ram be okay until I get another two crucial ram to match? or should I just ditch the apple ram for now?

View attachment 1712637

As you can see, your RAM isn’t working at full speed (2133 MHz instead of 2666 MHz) because you have mismatched RAM sticks.

If you need an additional 16 GB of RAM, pick the same Crucial modules. If 16 GB is enough for you, remove the Apple sticks.

 

[Bigyid]

As you can see, your RAM isn’t working at full speed (2133 MHz instead of 2666 MHz) because you have mismatched RAM sticks.

If you need an additional 16 GB of RAM, pick the same Crucial modules. If 16 GB is enough for you, remove the Apple sticks.

So it will do no harm leaving as is for next month or so?

 

[pldelisle]

So it will do no harm leaving as is for next month or so?

No.

 

[mikehalloran]

So it will do no harm leaving as is for next month or so?

Nope. It won't do any harm ever.

Although there is so much concern over speed, if your apps need more RAM, removing those sticks hurts overall performance.