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Yet Another Complication Upgrading Ram on Retina 5K, 27" 2020 iMac
- Thread starter jordii
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Maybe i missed it, but have you reset SMC and PRAM ?
SMC RESET
PRAM RESET
iMac SMC and PRAM reset
SMC RESET
- Shut down the computer.
- Unplug the computer's power cord from both the wall and computer.
- Wait 15 seconds.
- Attach the computers power cable.
- Wait another 5 seconds and press the power button to turn on the computer.
PRAM RESET
- Shut down the computer.
- Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
- Turn on the computer.
- Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
- Hold the keys down until the computer restarts and you hear the startup sound for the second time.
- Release the keys.
SMC Reset was accomplished multiple times as I futzed with the modules
PRAM reset didn't help.
Then show off your Firmware Version in the SystemReport 
Maybe you missed an MacOS Version and a critical Firmware Update to be compatible with these type of Ram.
Had this several Times with Mac´s.
Btw.: what MacOS are u using ?
The Other successful Users of these Crucial Ram´s could also post it to be sure.
Btw. i use Crucial Rams in many Mac´s and Hacky´s with no Problems.
If that does not help there might be a Problem with at least one of these Ram Modules leading to this....
As far as i can see you have done anything normally needet, also SystemReport shows identical charge Number...
Difference to the posted working Modules is also yours are showing much shorter info strings so what MacOS are you using ?
Maybe you missed an MacOS Version and a critical Firmware Update to be compatible with these type of Ram.
Had this several Times with Mac´s.
Btw.: what MacOS are u using ?
The Other successful Users of these Crucial Ram´s could also post it to be sure.
Btw. i use Crucial Rams in many Mac´s and Hacky´s with no Problems.
If that does not help there might be a Problem with at least one of these Ram Modules leading to this....
As far as i can see you have done anything normally needet, also SystemReport shows identical charge Number...
Difference to the posted working Modules is also yours are showing much shorter info strings so what MacOS are you using ?
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Firmware: 2020.80.3.0.0 (iBridge: 21.16.3030.5.2,0)Then show off your Firmware Version in the SystemReport
Maybe you missed an MacOS Version and a critical Firmware Update to be compatible with these type of Ram.
Had this several Times with Mac´s.
Btw.: what MacOS are u using ?
The Other successful Users of these Crucial Ram´s could also post it to be sure.
Btw. i use Crucial Rams in many Mac´s and Hacky´s with no Problems.
If that does not help there might be a Problem with at least one of these Ram Modules leading to this....
As far as i can see you have done anything normally needet, also SystemReport shows identical charge Number...
Difference to the posted working Modules is also yours are showing much shorter info strings so what MacOS are you using ?
MacOS: 14.2.1
Note that Software Update has not been offering new firmware (though it's of course now pushing MacOS 14.3)
Hardware system report below
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Just updated to MacOS 14.3, system firmware 2020.80.5.0.1 (iBridge: 21.16.3049.0.0,0)
....and memory data looks exactly the same.
I removed/reinstalled modules, too. Not sure if that triggered re-testing, or if the Mac recognizes the serial numbers and trusts its prior conclusions....
....and memory data looks exactly the same.
I removed/reinstalled modules, too. Not sure if that triggered re-testing, or if the Mac recognizes the serial numbers and trusts its prior conclusions....
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The 2020 is a little turd when it comes to RAM. OWC branded RAM won't make a difference, this was how I ended up getting mine to run them at full speed:
![Screenshot 2024-01-29 at 1.53.27 PM.png]( "Screenshot 2024-01-29 at 1.53.27 PM.png")
Apple sticks in slot 1/2, then the new sticks in 3/4.
Apple sticks in slot 1/2, then the new sticks in 3/4.
I already stated that RAM has channels which people either gloss over or say its wrong.
With regard to underclocked RAM it is also a thing, which I forgot about as I don't build PCs anymore.
It can be a thing that the RAM is not rated for what it says it is on the side of the box, which is why people buy from premium Mac specific RAM manufacturers like OWC.
Which on that note, also for these machines use the correct type of RAM which is LDDR. Specifically, low density, half height RAM sticks.
Other brands of RAM may work, or they may be the wrong speed, or not fit at all.
With this arrangement, 16GB will run in dual channel mode, and the remaining 24GB will run in single channel mode (which is effectively at half speed). This is known as "flex mode" per Intel. You cannot control which part of memory is being used by a particular process.
This is likely to result in slower overall memory speed than having all RAM running in dual channel mode but at 2133 MHz.
I can report that, as someone doing no rendering or compiling, 2133 MHz in dual mode is surely as fast as you probably need. I don’t feel any latency.
Here's a more detailed report, in case it's of interest to anyone.
FWIW, an OWC tech confirms the weird zeroed-out data for manufacturer and part number, says it all looks ok.
![SCR-20240201-oqyg.png]( "SCR-20240201-oqyg.png")
FWIW, an OWC tech confirms the weird zeroed-out data for manufacturer and part number, says it all looks ok.
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