Question changing CPU and lost half the ram

Aug 27, 2021

I came on tom's hardware because I found a lot of information here while digging into my issue
I know it will seem similar to other, but I didn't find or understand the solution for my problem.

I had this configuration
Asus Z170 Pro Gamin
Intel I5-6600k
4 x 4 GB Vengeance LPX 2666 Mhz (all identical)

I recently bought a I7-7700k to upgrade my configuration.

But then I can see All my four DIMMS in the Bios, but only half of it in the total:

My bios is up to date.
XMP profile is off.
I tried to clear the CMOS.
I tried sticks 2 by 2 it works fine on both dimms slots.
When I put back my I5-6600k I do have 16 Gb in total.
Of course in Windows 10 Pro I see only 8 Gb of Ram.

User Benchmark only sees 2 sticks:

When the CM detected a new CPU or if it boots on safe mode, I can see the tatal RAM correctly:

So it feels to me that my dimms and my socket are fine.
But I don't know if i didn't configure m y bios correctly or if my cpu is faulty.

I have looked around the internet and found many similar issues. But I never found a solution that worked for me.

Thank you in advance for you help.

Aug 27, 2021
Were the 4 sticks of ram part of 2 different sets?

Yes I bought 2 sets of 2 sticks separately with a year or two gap. But they are the exact same model and I've been running the four stick for four years now.
The problem just appeared when I changed the CPU.
If I put back my old CPU, it works fine with the four sticks.


Jan 25, 2020
Someone with more experience will have to verify this but that could be the problem. Does your PC show all 4 when XMP is off and 2 when it is on?
If the 6600K works, and the 7700K does not, it suggests to me that the 7700K may be defective.
It is most unusual to have a defective intel processor, but I encountered this once.

Be very careful when swapping processors.
It is easy to damage a socket pin if the cpu is not dropped in cleanly.
Such damage often results in ram issues.
Aug 27, 2021
Thanks for your help.
I was really cautious when I swap the CPU, and no pin appears to be bent on the socket.

Is there a way to check if it is the CPU or not ?
Would this explain why I can see the sticks in the "DIMM STATUS" in the bios, but not in "Memory". Is the second one controled by the IMC of the CPU ?
I don't want to file a reclamation on Ebay if it is my hardware that is not compatible.