iMac 2020 27" OWC memory incompatible with APPLE memory ???

[1brajesh]

I've ordered a new iMac 2020 27" (3.1GHz CPU version) and I went to order some 2x16G RAM from OWC.

However, they tell me I need to remove the base 2x4Gig Apple memory for the new OWC memory to work.
They said they have encountered issues where the Apple memory is not compatible with the new memory.

This sux. The mix and match should be compatible.
Anyone experienced this?
Why would this happen?
Anyone know which brand of memory will work with the existing apple memory so I don't lose 8 gigs?

 

[filmgirl]

See this thread (https://forums.macrumors.com/threads/memory-upgrade-troubleshooting-in-2020-27-inch-imacs.2249254/) and this one (https://forums.macrumors.com/threads/memory-upgrade-compatibility-list-for-imac-2019-2020.2248911).

OWC is correct and Apple’s own documentation now states this too. For whatever reason, the RAM is really sensitive this year. If you want to use the 8GB of Apple RAM you have two choices:

1. Install it in addition to the OWC RAM and have 40GB running at a slower clock speed but still in dual channel (so Apple RAM would remain in the slots it is in and you’d put the new RAM in the two open slots)
2. Install the RAM in alternating pairs (so Apple RAM in slots 1 and 2, OWC slots 3 and 4. The RAM will run at full speed but only in single channel, which will have a negative performance impact. This is not recommended.

If you want to run RAM at full capacity and in dual channel you need identically branded RAM and ideally, identically sized RAM.

It is unfortunate but that’s just the way it is. I suppose if you bought 32GB of RAM from Apple it might work, but considering how much Apple charges for its RAM that’s a bad idea. (And I’m not even sure that it would work, presumably Apple is installing in paired configurations for their BTO options). You can always start with the 32GB and then get two more sticks from OWC also sized 16GB in the future if you want to add more.

 

[iMi]

See this thread (https://forums.macrumors.com/threads/memory-upgrade-troubleshooting-in-2020-27-inch-imacs.2249254/) and this one (https://forums.macrumors.com/threads/memory-upgrade-compatibility-list-for-imac-2019-2020.2248911).

OWC is correct and Apple’s own documentation now states this too. For whatever reason, the RAM is really sensitive this year. If you want to use the 8GB of Apple RAM you have two choices:

1. Install it in addition to the OWC RAM and have 40GB running at a slower clock speed but still in dual channel (so Apple RAM would remain in the slots it is in and you’d put the new RAM in the two open slots)
2. Install the RAM in alternating pairs (so Apple RAM in slots 1 and 2, OWC slots 3 and 4. The RAM will run at full speed but only in single channel, which will have a negative performance impact. This is not recommended.

If you want to run RAM at full capacity and in dual channel you need identically branded RAM and ideally, identically sized RAM.

It is unfortunate but that’s just the way it is. I suppose if you bought 32GB of RAM from Apple it might work, but considering how much Apple charges for its RAM that’s a bad idea. (And I’m not even sure that it would work, presumably Apple is installing in paired configurations for their BTO options). You can always start with the 32GB and then get two more sticks from OWC also sized 16GB in the future if you want to add more.

#nailedit. There is nothing else to add to it. You covered it 100%. I also looked into and and glad I did. I ordered larger set knowing I couldn’t pair them with the one from Apple.

 

[fronesis]

EDIT: It's pretty clear that while the machine will boot and run fine, the performance is compromised by having non-matching sizes. My ram was running at the lower clock speed; removing the 4Gb chips returned to full speed.

I have a 2020 iMac 27" with the same stock RAM as yours.
I ordered the exact OWC memory you are looking at (2x16GB).
Multiple reviewers on Amazon said to MOVE the stock apple ram from the original slots to the two open slots, then put the OWC ram in the now-open slots.

I did that.

The machine has run perfectly for the past 3 weeks.

 

[filmgirl]

I have a 2020 iMac 27" with the same stock RAM as yours.
I ordered the exact OWC memory you are looking at (2x16GB).
Multiple reviewers on Amazon said to MOVE the stock apple ram from the original slots to the two open slots, then put the OWC ram in the now-open slots.

I did that.

The machine has run perfectly for the past 3 weeks.

Don’t do this. It will “work” but your RAM is now running in single channel and that will impact performance. If that trade-off is OK with you, awesome. Most of us would rather the RAM run at a lower clock speed or have less of it installed than have it running in single channel mode. The difference is most notable in RAM optimized applications like Photoshop and in games.

Again, if people understand the trade-offs and want to do this anyway, that’s totally cool. But many of us here are trying to educate people about what those trade-offs are.

 

[4743913]

I've ordered a new iMac 2020 27" (3.1GHz CPU version) and I went to order some 2x16G RAM from OWC.

However, they tell me I need to remove the base 2x4Gig Apple memory for the new OWC memory to work.
They said they have encountered issues where the Apple memory is not compatible with the new memory.

This sux. The mix and match should be compatible.
Anyone experienced this?
Why would this happen?
Anyone know which brand of memory will work with the existing apple memory so I don't lose 8 gigs?

Just toss the 8GB or eBay it. It's not worth the impact to your system in any way. you got 32GB. Don't be greedy.

 

[1brajesh]

@fronesis glad to see there is some hope!

@filmgirl thanks your response is helpful for me to know that this is a documented issue. I think memory is not usually the biggest bottleneck. Do you know where I can find what performance reduction occurs with the method that @fronesis suggests so I can make an informed decision for my needs?

 

[wilberforce]

I have a 2020 iMac 27" with the same stock RAM as yours.
I ordered the exact OWC memory you are looking at (2x16GB).
Multiple reviewers on Amazon said to MOVE the stock apple ram from the original slots to the two open slots, then put the OWC ram in the now-open slots.

I did that.

The machine has run perfectly for the past 3 weeks.

Yes, it runs, but not "perfectly." MaxTech investigated this in their Youtube video, for example. The results clearly show that mixing different sizes of RAM, no matter how you arrange it, degrades performance. This has been confirmed by multiple people, myself included. (If you really need more than 32GB, suggest get 64GB of matched sticks.)

See 7:02 in their video for explanation:

 

[1brajesh]

This video is super helpful, thank you @wilberforce

 

[fronesis]

I stand corrected!

 

[1brajesh]

Thanks, what confirmed it @fronesis ?

 

[fronesis]

Thanks, what confirmed it @fronesis ?

Just the video that Wilberforce posted above: it's pretty conclusive.

For the record: I was *not* running my setup in single channel mode, because I didn't put the same sizes in adjacent slots, but my ram was throttled back to the slower rate – and I'm sure the video benchmark results were affecting me.

For me the difference between 40Gb and 32Gb will be completely imperceptible. I had just left the original apple 4Gb chips in because I didn't think they'd be of much value on eBay and I had no other use for them.

 

[1brajesh]

So are the slots numbers labeled on the iMac 2020?
How does the single channel / dual channel and slot position work?

 

[fhopper]

Would you like the two Apple sticks I just pulled from my 2020? You are welcome to them. New machines are very expensive and you are welcome to my 2X4Gb Apple sticks. You could then wait a bit before buying a set of four new bigger sticks.
BTW my 4 matching sticks from OWC work great. I tried putting all in at once but she went into an early power up loop, not sure I would have heard it if an external drive wasn't powering on and off. So I put
two sticks in the slots Apple used, zapped the PRAM and she booted fine. Next I simply added the other two sticks and she booted fine... and has ever since.

 

[wilberforce]

So are the slots numbers labeled on the iMac 2020?
How does the single channel / dual channel and slot position work?

Slots in 2020 iMac are not physically labeled but are 1 to 4, top to bottom.
Slots 1 and 2 are Channel A, Slots 3 and 4 are Channel B.
For dual channel, you want same size sticks in Channel A and Channel B (thus the memory controller can access channels A and B in parallel).
If you have two matching sticks, fill slots 2 and 4 first (as these are the DIMM 0 slots)
If you have four sticks, have them all the same size.

You can check what is in each slot and channel by going to:

About this Mac
System Report
Hardware
Memory

 

[fhopper]

Slots in 2020 iMac are not physically labeled but are 1 to 4, top to bottom.
Slots 1 and 2 are Channel A, Slots 3 and 4 are Channel B.
For dual channel, you want same size sticks in Channel A and Channel B (thus the memory controller can access channels A and B in parallel).
If you have two matching sticks, fill slots 2 and 4 first (as these are the DIMM 0 slots)
If you have four sticks, have them all the same size.

You can check what is in each slot and channel by going to:

About this Mac
System Report
Hardware
Memory

My machine shipped with the Apple 2X4Gb in the bottom slot and next to top slot. I have read Apple ships a two stick machine with the RAM in slots 1 and 3. That lead me to think the bottom slot is slot 1... Matching sticks making it fully functional.

 

[wilberforce]

My machine shipped with the Apple 2X4Gb in the bottom slot and next to top slot. I have read Apple ships a two stick machine with the RAM in slots 1 and 3. That lead me to think the bottom slot is slot 1... Matching sticks making it fully functional.

No, top slot is slot 1. The 2020 iMac ships with apple sticks in slots 2 and 4

 

[RichiMac]

That is all well and good, but here is my similar, but different problem.

I got the new 27" iMac and maxed it out, except for ram and SSD (went for 2T, so still pretty max). I replaced the minimum Apple ram with the recommended OWC 128g ram (32X4). I did this before I even set up my new iMac. Since then I have been plagued with random freezes, shut-downs, and restarts. Sometimes I get the "your computer was shutdown because of a problem" notice, sometimes not. Here's some of what I have down so far: 1) eliminated a lot of old files and software, 3) virus scans, several times (malwarbytes, recommended to me by apple, found 4 small viruses, but nothing since in the last few weeks), 4) did a complete reinstall of mac OS X, 5) removed OWC ram, and used the apple ram for a few days (this seemed to work, but of course everything was a bit slower), 6) contacted OWC and got my ram replaced, as defective, and 7) installed the 128g of replacement ram from OWC. Now, I have not had any more freezes, but all the other restart issues have returned. I have had 3 separate phone conferences with apple phone techs about these issues (established a service ticket). The last one today to tell them how replacing ram only eliminated freezing (so far, anyway), but now it either restarts or is completely shut down and hard to restart every morning. I have also done other things, too numerous to mention, but these are the major steps I have taken.

NOW APPLE SAYS that they have had service tickets involving 3rd party ram issues, but their engineers won't even look at a computer if the ram issue is from a 3rd party. This last was from a "senior advisor" who came to the phone when I told the tech who answered all that I have already done. My only recourses are....buy expensive apple ram and hope it works, reinstall OS X, but don't reinstall my data, start clean and see if it happens (that eliminates a lot of data and ram use, so I am skeptical that will prove anything), hire a private computer service to analyze and troubleshoot, or buy ram from another company than OWC and hope it works (if I can get a refund from OWC at this point...it has been a couple months).

Sorry for the long post, but I can't find anything online anywhere that speaks to my particular issues.
Thanks for any suggestions.

 

[1brajesh]

@RichiMac sorry to hear.
Mine is working fine with 32gig from OWC (2x16) which I put in the same slots in which was the apple RAM.

I sometimes have to call a few different apple support guys until I get a nerdy one who ignores the "apple rules".
Try calling at different times to get better support?

Also, try going down to two sticks of RAM and see if things improve.

And last resort, exchange the MAC, you might have got a defective one?

 

[RichiMac]

@RichiMac sorry to hear.
Mine is working fine with 32gig from OWC (2x16) which I put in the same slots in which was the apple RAM.

I sometimes have to call a few different apple support guys until I get a nerdy one who ignores the "apple rules".
Try calling at different times to get better support?

Also, try going down to two sticks of RAM and see if things improve.

And last resort, exchange the MAC, you might have got a defective one?

I have called different times. I have spoken with 3 different techs for an average of an hour each. An each have read through the notes of the others before them. None of them have cut me off. I am always the one to end the call after we run out of options. Then they offer a call back if necessary.

I cannot exchange the mac. I have had it beyond the exchange period. I ordered it when they first came out. And since they cannot verify it is an apple issue, they won't do any warranty exchange or replacement. It was a special order through Ireland. It is fully maxed out except for ram and SSD.

I do like the idea of trying just 2 of the sticks at a time, and was thinking of that as well.

Thanks for replying.

Has anyone else out there maxed their ram?????