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New 2020 5k iMac having trouble with 4 new dimm sticks. 3 new +1 OEM work just fine. :o

manhattanmac

macrumors newbie
Original poster
Aug 17, 2020
2
0
Howdy,

I bought a 64gb ram upgrade kit from OWC for my brand new 2020 5k iMac, 27 incher. However, strange boot issues abound when I try to install all 4 sticks at once.

2 OEM sticks and 2 empty slots = boot normally
1 OEM stick + 3 OWC sticks = boot normally
4 OWC sticks = failed boot

When the boot fails, I get only a black screen. The display doesn't power on at all, but I can hear the fan try to spin up every 30 seconds or so, but only spins for maybe 1 second and then spins down again. This process repeats until I pull the power cable. I've also tried just about every configuration to see if I have a faulty OWC stick, or a faulty RAM slot. Every OWC stick works by itself. Every RAM slot works by itself. It's just that weirdly, installing all 4 OWC sticks causes a failed boot even though no single stick is bad.

Does anyone have any thoughts as to what is causing this or a potential solution?

Thanks!
 

mindquest

macrumors 6502
Oct 25, 2009
430
94
Howdy,

I bought a 64gb ram upgrade kit from OWC for my brand new 2020 5k iMac, 27 incher. However, strange boot issues abound when I try to install all 4 sticks at once.

2 OEM sticks and 2 empty slots = boot normally
1 OEM stick + 3 OWC sticks = boot normally
4 OWC sticks = failed boot

When the boot fails, I get only a black screen. The display doesn't power on at all, but I can hear the fan try to spin up every 30 seconds or so, but only spins for maybe 1 second and then spins down again. This process repeats until I pull the power cable. I've also tried just about every configuration to see if I have a faulty OWC stick, or a faulty RAM slot. Every OWC stick works by itself. Every RAM slot works by itself. It's just that weirdly, installing all 4 OWC sticks causes a failed boot even though no single stick is bad.

Does anyone have any thoughts as to what is causing this or a potential solution?

Thanks!
Did you call OWC and work with tech support on it yet? They have a really good support team. Let us know what you find out.
 
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mechapreneur

macrumors newbie
Aug 17, 2020
7
5
I have had the exact same problem. Booted the iMac with OEM RAM, fine. Replaced with 4x32GB and it wouldn't pass the memory test. It just spun the fan every 30 seconds for 1 second and repeat. Drove me nuts. I thought I had nailed it down to a bad DIMM slot in the iMac, but then I tried the OEM sticks in slots 1 (bad) and slot 3 and the iMac booted.

But then it got weirder. Running on the OEM RAM in slot 1 and 3, I couldn't install a requested Catalina Supplemental Update. It would download, reboot to install, but then fail and reboot again only to post the message that my iMac crashed and then continue booting. Again I would be told there was a supplemental update for Catalina waiting for me.

I switched back to OWC RAM in slots 2 & 4 (good slots) and would get the same problem during the Catalina update's reboot.

Apple Tech support seemed to agree it might be a hardware problem and suggested SMC reset (which happens when you replace RAM) and re-install the OS. We booted to Recovery partition, ran First Aid on both volumes (HD & HD Data) and then re-installed Catalina which included the supplemental update I was told.

After running benchmarks and other heat stress loads, I decided to try all four OWC DIMMs again and ... for reasons I don't understand, the system booted fine. I've since done many, many reboots trying to get the prior condition to recur, but it seems stable in this configuration. Maybe I switched the DIMMs around in the slots and randomly found a combination that the iMac liked.

I still want to talk to OWC support and see if this could be something else before my return window expires. I hope this story helps others who are going crazy.
 
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Donnation

Suspended
Nov 2, 2014
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I have a question that is not super related but wanted to see if i could get a quick answer. I have 2X32 Sticks coming for my new iMac (2020). I’ve replaced RAM many times on machines I’m currently using but never a brand new one. Do I need to boot the machine first before install the new RAM? Or can I just install the new RAM and then boot the machine for the first time.
 
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Hulip

macrumors newbie
Sep 23, 2017
16
6
Howdy,

I bought a 64gb ram upgrade kit from OWC for my brand new 2020 5k iMac, 27 incher. However, strange boot issues abound when I try to install all 4 sticks at once.

2 OEM sticks and 2 empty slots = boot normally
1 OEM stick + 3 OWC sticks = boot normally
4 OWC sticks = failed boot

When the boot fails, I get only a black screen. The display doesn't power on at all, but I can hear the fan try to spin up every 30 seconds or so, but only spins for maybe 1 second and then spins down again. This process repeats until I pull the power cable. I've also tried just about every configuration to see if I have a faulty OWC stick, or a faulty RAM slot. Every OWC stick works by itself. Every RAM slot works by itself. It's just that weirdly, installing all 4 OWC sticks causes a failed boot even though no single stick is bad.

Does anyone have any thoughts as to what is causing this or a potential solution?

Thanks!

did You call them? Ordered same memory configuration from owc. Waiting for memory and mac to arrive. This is concerning.
 
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gilby101

macrumors 6502
Mar 17, 2010
392
157
Tasmania
I have a question that is not super related but wanted to see if i could get a quick answer. I have 2X32 Sticks coming for my new iMac (2020). I’ve replaced RAM many times on machines I’m currently using but never a brand new one. Do I need to boot the machine first before install the new RAM? Or can I just install the new RAM and then boot the machine for the first time.

I am sure you can just install the extra RAM and boot first time. But, I would always run the iMac for a day or so with the out of the box configuration just to nail any obvious Apple hardware issues. Given the issues people are having when adding not fully compatible RAM, I would want to be doubly sure that the Apple configuration was stable before adding RAM.
 
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Donnation

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Nov 2, 2014
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I am sure you can just install the extra RAM and boot first time. But, I would always run the iMac for a day or so with the out of the box configuration just to nail any obvious Apple hardware issues. Given the issues people are having when adding not fully compatible RAM, I would want to be doubly sure that the Apple configuration was stable before adding RAM.

Thank you!
 
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Donnation

Suspended
Nov 2, 2014
1,686
2,065
FYI I opened my 2020 iMac out of the box and immediately removed the Apple RAM and put in my third party RAM (4x 8 GB chips) and booted it for the first time that way, no issues.

Oh that’s really good to know, and that’s what I’d prefer to do. Thank you!
 
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Mikeeee

macrumors 6502
Sep 27, 2017
458
285
FYI I opened my 2020 iMac out of the box and immediately removed the Apple RAM and put in my third party RAM (4x 8 GB chips) and booted it for the first time that way, no issues.

Is 4 x 8 better then 2 x 16. If so, why?
 
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PBG4 Dude

macrumors 68040
Jul 6, 2007
3,128
2,473
I had a slightly better deal for the 4x 8 GB chips so that is the only reason that I went that route, and that I probably won't be upgrading to 64 GB anytime soon.

If you do 2x 16 GB chips make sure to put them in the 1 and 3 slots for dual-channel efficiency.
I almost want to upgrade to 64GB just so I’ll never have to worry about being short of RAM.
 
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mechapreneur

macrumors newbie
Aug 17, 2020
7
5
OWC Support mentioned this hint:
the Newer imac models do require, when only two modules are installed, to be installed into specific slots. Often the two slots the Apple RAM came installed into.
Which could explain why my new DIMMs did not work in slots 1,3 as a pair, but worked in slots 2,4 as a pair since those were the same slots the OEM modules arrived in.

This doesn't explain all my problems, but does explain some of them.
 
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mechapreneur

macrumors newbie
Aug 17, 2020
7
5
FYI, OWC support is great. I'm glad they have a lifetime warranty on these DIMMs because... my 2020 iMac is dead/dying and won't boot or stay up, even running the original DIMMs from Apple. So the iMac going back to Apple today and I have to order another one.
 
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MMidnight

macrumors newbie
Aug 10, 2020
16
11
OWC Support mentioned this hint:

Which could explain why my new DIMMs did not work in slots 1,3 as a pair, but worked in slots 2,4 as a pair since those were the same slots the OEM modules arrived in.

This doesn't explain all my problems, but does explain some of them.
That’s weird I have my 2x32gb in slots 1 & 3 as those were where I had higher benchmark scores and are working perfect ...
 
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mechapreneur

macrumors newbie
Aug 17, 2020
7
5
Just to tie this off: I got my replacement iMac last week and had zero problems upgrading all four DIMMs with the same OWC modules I tried the first time. I started with 2x32 in slots 1 and 3, replacing the OEM DIMMs. Booted up with 64GB just fine. Then I added two more to the open slots and now have 128GB. My first order was clearly having logic board issues.

I will mention that I thought my performance was off since Geekbench 5 multicore was consistently low (<8,200) running at 8GB RAM, but sped up nicely when I upgraded to 64GB (10,001). A clear and repeatable 25% improvement. The memory upgrade is definitely a good return on investment.
 
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wavesm

macrumors member
Oct 13, 2019
60
10
Just to tie this off: I got my replacement iMac last week and had zero problems upgrading all four DIMMs with the same OWC modules I tried the first time. I started with 2x32 in slots 1 and 3, replacing the OEM DIMMs. Booted up with 64GB just fine. Then I added two more to the open slots and now have 128GB. My first order was clearly having logic board issues.

I will mention that I thought my performance was off since Geekbench 5 multicore was consistently low (QUOTE]

Did you see any improvement going from 64 to 128?

I have 64 but thinking on getting another 64 to be covered on future compatibility issues.
 
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mechapreneur

macrumors newbie
Aug 17, 2020
7
5
I saw no significant or repeatable improvement going from 64GB to 128GB. I bought the extra DIMMs solely for future proofing and to ensure all four slots worked before my return/warranty windows expire.
 
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wavesm

macrumors member
Oct 13, 2019
60
10
Thanks, also considering that but still not sure whether really need the 128.

Very rarely I get mem pressure about 70% with 64GB
 
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manhattanmac

macrumors newbie
Original poster
Aug 17, 2020
2
0
Been a while, but I was able to fix the issue by calling OWC and having them send replacement ram. For some reason, the replacement ram worked fine. Still not sure why.
 
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