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I have a iMac Retina 5k 27-inch, Late 2016 version. Checked physically there are 2pcs 8GB 1867 MHz DDR3 RAM and for whatever reason, dont know since when, it shows only 1 physical RAM in use. I have recently bought 2pcs new 8GB RAM with same specification but fail to add.
Confirmed the new RAMs purchased are in good condition by taking out the old RAM at slot 1 & 3.
iMac 27″, macOS 11.2
since it's not detecting detecting the RAM in one of the slots, you may have a hardware issue. first try putting the original RAM in slots 1 & 2 then put the OWC RAM in slots 3 & 4. and re boot.
if that doesn't work, run diagnostics. >> Use Apple Diagnostics to test your Mac - Apple Support
since it's not detecting detecting the RAM in one of the slots, you may have a hardware issue. first try putting the original RAM in slots 1 & 2 then put the OWC RAM in slots 3 & 4. and re boot.
if that doesn't work, run diagnostics. >> Use Apple Diagnostics to test your Mac - Apple Support
iMacs are EXTREMELY sensitive to using very high quality RAM. Most experienced users on these forums recommend either Crucial.com or Macsales.com RAM. Why, simple...reasonable pricing, they products work, lifetime guarantees and great support.
So exactly what RAM did you buy and from who?
Your are absolutely right. I made a mistake and there is a typo. It should be 2015.
I bought a OWC performance memory from a local dealer name icertified. The problem is not the RAM. The new RAM working fine at slot 0 and 2. Assuming the slots naming is 0, 1, 2, 3.
I have taken out the original RAM installed from factory at slot 0 & 2. Just to ensure that the new RAM is working fine.
However, the memory that the system shows is still 8 GB at slot 0.
My best guess is that the slot is having issue?
Your are absolutely right. I made a mistake and there is a typo. It should be 2015.
I bought a OWC performance memory from a local dealer name icertified. The problem is not the RAM. The new RAM working fine at slot 0 and 2. Assuming the slots naming is 0, 1, 2, 3.
I have taken out the original RAM installed from factory at slot 0 & 2. Just to ensure that the new RAM is working fine.
However, the memory that the system shows is still 8 GB at slot 0.
My best guess is that the slot is having issue?
Oh one more thing. I tried to put all 4 memories like the following order:-
Original 8GB RAM - Slot 0
New OWC 8GB RAM - Slot 1
Original 8GB RAM - Slot 2
New OWC 8GB RAM - Slot 3
The system didnt startup at all.
Original 8GB RAM - Slot 0
Empty - Slot 1
Original 8GB RAM - Slot 2
Empty - Slot 3
System can boot successfully but system only shows 8GB at Slot 0 and others slot shows empty.
New OWC 8GB RAM - Slot 0
Empty - Slot 1
New OWC 8GB RAM - Slot 2
Empty - Slot 3
System can boot up properly and works normally. But only showing 8GB at slot 0, other slots shows empty.
Thanks a lot. Problem resolved with new RAM installed at slot 2 & 4. Total 16GB of RAM working properly. After that I tried to add 2 more old RAM but failed. Finally I add one more old RAM at slot 1 to make it 24GB in total.
so probably there’s a hardware issue at slot 3. But I have never been able to initiate the hardware diagnose.
Exactly what RAM did you buy and from whom did you buy it?
Also there is no 2016 iMac. They jumped from iMac Late 2015 to iMac 2017. What does "About this Mac..." show for your sub-model?
added a diagram to my previous post
RAM expansion issue
