27" iMac new 16 gb memory restart

[McHeenan]

I have 8 gb of memory. I replaced them with 2 16gb pc4-21300 sodimm 2rxb cl19 1.2v memory sticks from ADAMANTA. My machine does a restart every once and awhile now. I am well within specs. Has anyone delt with this problem? I put the two fours back in and had the Apple Genious Bar do a thorough 3 day diagnostic on the total system and passed everything. I now have baseline I can trust.

 

[wilberforce]

I assume this is a 2019 or 2020 iMac?
You could try a process of elimination.
Take out the 4GBs and put in only one of the 16GB sticks.
If that works, try the other 16GB stick.

I realize this is far from an optimal memory arrangement, as you should use matched pairs for optimal performance, but it will still run. Unless one of the DRAMs is faulty (or a slot is faulty, or the slot/DRAM contacts are faulty).

 

[McHeenan]

Thanks...I have tried just the 2 16GB sticks and after about 15 min. it will restart.
I had apple do all the tests on hardware and software with my original 8GB of Ram and it passed. I wanted to eliminate as much as I can. I think it just comes down to incompatible sticks.

 

[wilberforce]

I can recommend these. Crucial have the best reputation for DRAMs. This is what I have in my 2020 iMac

Crucial 32GB Kit (16GBx2) DDR4 2666 MT/s (PC4-21300) CL19 DR x8 SODIMM 260-Pin for Mac - CT2K16G4S266M

CT2K16G4S266M is a 32GB Kit consisting of (2) 16GB Dual Ranked DDR4 SODIMM modules that operates at speeds up to 2666 MT/s and has a CL19 latency. It is an Unbuffered SODIMM. It conforms to the industry standard DDR4 SODIMM layout of 260 pins and is compatible with systems that take DDR4 2666MT/s...

www.amazon.com

 

[Fishrrman]

IF you have unwanted reboots with the NEW RAM,
and
IF things go back to normal when you put the factory RAM back in,
then
I would suspect the new RAM.

It doesn't matter if it's "within specs". It doesn't work.

I'd order new RAM (I suggest Crucial), and return the non-working RAM.

 

[CWallace]

I have the same memory in my 2020 iMac 5K and no issues whatsoever, so my guess is one of the DIMMs is bad and needs to be replaced.

 

[briloronmacrumo]

Yep, almost certainly bad DIMMs. I"ve also had good luck with Data Memory Systems.

 

[Fishrrman]

Agree with post 7 above.
Good luck with DMS here, too.