iMac 2020 ram upgrade issues

[Pipengue]

Hello, I think I have a problem with the compatibility of ram memory modules in the iMac 2020.

Although all modules are of the same brand (Crucial) the same capacity (8gb) and the same clock speed (2666mhz) “see photo” when installed, the system does not work at the indicated speed but at a lower speed (2133 mhz)

Apple's official information is that these three aspects must match: the same speed, brand and size but

When looking at each module, the only difference I find is that one of the memory sticks has 16 memory chips instead of having 8 ram modules like the others, this according to the Linus Tech Tip video where he warns how manufacturers do this type of tricks.

I do not know if any of you can recommend me in this case, if I can try something different to get the iMac to work at the maximum speed indicated by the memory modules.

 

[wilberforce]

The 2020 iMac is very fussy: the part numbers for sticks in slots 1 and 2 must exactly match, and the part numbers for sticks in slots 3 and 4 must exactly match, else speed drops to 2133.
Also for full dual channel the size of sticks in slots 1 and 3 must be the same, and the size of sticks in slots 2 and 4 must be the same.
The problem is you have sticks with 3 different part numbers. It is therefore impossible to satisfy both the above requirements.
You need to have all sticks the same size (which you do), and you need to have a pair of sticks exactly identical to each other, and the other pair of sticks exactly identical to each other (but not necessarily identical to the first pair).
It is big mystery why this weird requirement for the 2020 imac (and only the 2020 imac), but it is just the way it is.
Your ram that you have will work, just not optimally

 

[PBG4 Dude]

There’s a huge thread that delved into how finicky RAM is in the 2020 iMac. The previous poster covered all the main points that came from that thread.