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Memory upgrade troubleshooting in 2020 27-inch iMacs

tonywalker23

tonywalker23

macrumors 6502a
Dec 21, 2003
508
1,543
SC
I got my new iMac yesterday. Came with standard 8gb and booted fine. I then installed 32 (16x2)gb from OWC. It stayed black for a while. Made some fan noise. I eventually pressed the power button again. Eventually booted and showed a kernel panic. Rebooted and it got to the OS and it showed 40gb. I noticed the lower speed and removed the Apple ram leaving the 2 OWC sticks. Couldn't get it to boot. I then switched the two OWC sticks into where the apple sticks used to be. Then booted, showed 32gb, and at 2667 speed. Think I will leave well enough alone and try this. I booted into the Hardware test holding D while booting and it said it had no erros.

Question, can I take the two apple sticks and put them into some empty slots on a 2015 iMac? Forgive my ignorance but would it just slow the newer ram down to work or do I risk messing anything up physically/electronically?
 
anthony13

anthony13

macrumors 65816
Jul 1, 2012
1,053
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I have 32gb (two sticks of 16) of Crucial coming in the mail, to add to my stock 32gb I got at purchase (two 16gb sticks of Micron). The hope is that because my ram is Micron and not Hynex, that it might play better with Crucial (which also uses Micron). They're the same size, and all dual rank. I know it's unlikely it won't bottle neck it, but I can always return it, and this should be a fun experiment to see if we can eliminate size or manufacture differences from the bottle neck issues.
 
A

Azrael9

macrumors 68020
Apr 4, 2020
2,287
1,835
I put the two 16 gigs sticks from Crucial into the 'Apple' RAM slots and left well enough alone.

The RAM door is very tetchy.

My two 4 gig sticks are in storage. (I did try the 40 gigs of RAM. But I lost dual channel speed. So did as above.)

Azrael.
 
minik

minik

macrumors demi-god
Jun 25, 2007
2,212
1,744
somewhere
I received the iMac yesterday and immediately replaced the stock (2x4GB memory) with the Crucial brand 32GB kit onto slot 2 and 4. No issue so far. The stock Apple memory also has the Micron logo.

IMG_0162D.jpeg
 
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pldelisle

pldelisle

macrumors 68020
May 4, 2020
2,248
1,506
Montreal, Quebec, Canada
minik said:
I received the iMac yesterday and immediately replaced the stock (2x4GB memory) with the Crucial brand 32GB kit onto slot 2 and 4. No issue so far. The stock Apple memory also has the Micron logo.

View attachment 947451
Click to expand...
For sake of this forum, could you please try adding the Apple kit into the slot 1 and 3 and perform GeekBench 5 benchmark and show us in the system report the working RAM speed ?
 
jasnw

jasnw

macrumors 65816
Nov 15, 2013
1,032
1,134
Seattle Area (NOT! Microsoft)
I think all of us who are lurking on this thread would like to see some sort of common testing and reporting. This is thread is a huge help, but it's hard to keep track of what has worked all the time, what has worked some of the time, and what hasn't worked at all. Not to mention different measures of what "working" means.
 
anthony13

anthony13

macrumors 65816
Jul 1, 2012
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jasnw said:
I think all of us who are lurking on this thread would like to see some sort of common testing and reporting. This is thread is a huge help, but it's hard to keep track of what has worked all the time, what has worked some of the time, and what hasn't worked at all. Not to mention different measures of what "working" means.
Click to expand...
To summarize, I'm fairly certain that anything short of removing the apple ram has not worked. No one has successfully kept dual channel and 2666MHZ by combining Apple Ram and aftermarket ram (that I know of). In general you want to buy Crucial, OWC or Samsung RAM, and if you remove the apple RAM, you should be good to go. Tomorrow I'll be reporting back my findings, which is to test stock Apple Micron Ram with Crucial ram (and all the same size, 16GB). That however is a somewhat rare case, as most people did not upgrade RAM from the Apple directly at the time of purchase, as I did.
 
jasnw

jasnw

macrumors 65816
Nov 15, 2013
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So you will be trying twoX16GB from Apple and two from Crucial for a total of 64GB? That should be interesting - I'm thinking of doing twoX8GB from Apple and two from Crucial for 32GB. Another option I'm thinking about (and I think someone was going to test this) is get twoX4GB from Apple and buy two discarded 4GB from some 2020 iMac owner. I don't really need 32GB,
 
pldelisle

pldelisle

macrumors 68020
May 4, 2020
2,248
1,506
Montreal, Quebec, Canada
jasnw said:
So you will be trying twoX16GB from Apple and two from Crucial for a total of 64GB? That should be interesting - I'm thinking of doing twoX8GB from Apple and two from Crucial for 32GB. Another option I'm thinking about (and I think someone was going to test this) is get twoX4GB from Apple and buy two discarded 4GB from some 2020 iMac owner. I don't really need 32GB,
Click to expand...
He is trying this because his stock RAM is from Micron and chances are both stock and Crucial RAM have the same DRAM ICs on them.

If your iMac came with Hynix RAM, you don’t have choice to discard them.
 
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DQ11

DQ11

macrumors regular
Apr 12, 2018
199
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What way do I install the RAM? It looks like one side is longer. From the videos it looks like Longer side is on right but on apple's website the wording makes it sound different?
 
pldelisle

pldelisle

macrumors 68020
May 4, 2020
2,248
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Montreal, Quebec, Canada
DQ11 said:
What way do I install the RAM? It looks like one side is longer. From the videos it looks like Longer side is on right but on apple's website the wording makes it sound different?
Click to expand...
There is only one way ....... The other way you'll need a hammer to put the RAM in ....... I don't recommend this way.
 
hellfried

hellfried

macrumors regular
May 3, 2008
127
14
Penang, Malaysia
DQ11 said:
What way do I install the RAM? It looks like one side is longer. From the videos it looks like Longer side is on right but on apple's website the wording makes it sound different?
Click to expand...
Learnt this from a YouTube video. The notch is off set to one side. Always aim the notch so that it is nearest to where the I/O ports are located on the back of the iMac.
 
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DQ11

DQ11

macrumors regular
Apr 12, 2018
199
65
hellfried said:
Learnt this from a YouTube video. The notch is off set to one side. Always aim the notch so that it is nearest to where the I/O ports are located on the back of the iMac.
Click to expand...
Just found 2 more videos showing same. Thanks for confirming.
 
anthony13

anthony13

macrumors 65816
Jul 1, 2012
1,053
1,199
Man I really hate returning this... this is keeping the original apple ram in 2 and 4, and putting the new ram in 1 and 3. So that's apple stock 16GB Micron Ram sticks in 2 and 4, and new crucial micron ram sticks in 1 and 3.

Screen Shot 2020-08-26 at 3.57.37 PM.png
 
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