iMac13,2 27" with firmware from 21.5" not seeing the 4 memory bays

No, i doesn't help.

Because not the type of memory is a problem:

We have 4 bays. I take 2 modules and I put them in bay 1&2 - iMac starts. I take the same modules but put them in bay 3&4 leaving the bay 1&2 empty - iMac gives an error.

I tried many combinations with many types of memory and I concluded that the problem is with the firmware which doesn't work with 4 memory bays. I welcome any other ideas of course thats why I wrote my situation here.

The RAM I am putting is the Kingston HyperX HX316LS9IB/8 - and it works when I put 2 of them in the bay 1&2.

I tried also other types, with 4GB, 2GB - all of them work in basically any combination but ONLY in bay 1&2. Touching bays 3&4 sends all the iMac into the error zone.

My model is somewhat strange one and I can believe nobody may have stumbled upon such thing until now... But on the other hand I bought this model to put 32GB of mem inside... it's barely 2 years old model!

So to clear things up:

any of the 4 memory modules work fine if I populate only bay 1&2. You can see on the system report I posted I have 16GB memory - its the 2x8GB. I tried to put 4 of them together - doesn't work. I try to put some combination like bay 3&4 or bay 1&3 - NOTHING works if ANYTHING is in any of the 3&4 bays. So the bay 3&4 must have something to do with the issue - either its a hardware failure of the bays (has anybody HAD a problem like this because I have never ever had in my very long experience...) or its a EFI which thinks it has only 2 bays (like on the 21.5" iMac).

Like i say I also have hundreds of other memory modules of different types and speeds and they all work fine only in bay 1&2 - whatever touches bay 3&4 makes the iMac stop to work.

The beeps are the "memory failed test".

But ALL of these hundreds that I tested DO WORK in this iMac. As long as I put them in bay 1&2 and leave bay 3&4 empty.

I also have the original 2x8GB Hynix which came from the factory and they also work only in the bay 1&2.

I believe that the firmware is supposed to work for both 21.5" and 27" version of late 2012 iMac - but who can guarantee there is not an error in the firmware since I have a rare made-to-order configuration. And there is NO firmware at all at Apple site - 27" iMac13,2 doesn't exist at all for Apple.

iMac 27 (Late 2012) Shuts down. #2

As you may see in this thread, the same iMac with the same firmware DOES work with 4x4GB memory.

So at least the firmware has been proven to be correct and I can abandon this lead.

Still it only proves that 16GB is supported. I will try the same 4x4GB configuration tomorrow from another iMac I have - to address the memory quality issue.

Like I say the iMac WORKS with 2xKingston memory so it would be actually surprising why 4 of the same modules would cause an issue. And all memory modules I tried I took from working iMacs so they are tested... (I tried 2GB, 4GB, 8GB modules from 4 different producers)

But I will return to the issue again with other modules tomorrow. Any more ideas welcome (for example how to verify if there is a damaged memory bay without opening the iMac?).