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Z690E boots with only a single DIMM in B2 slot

Level 8

I just purchased a Z690E motherboard.  For the CPU, I purchased the i1-12900KF and for memory, I got the Corsair Vengeance 2x32 GB DIMMs.  Both the CPU and the memory are listed on the motherboard compatibility list.  At first, I could not even boot the machine.  I then updated the BIOS using the USB stick method.  After this, I started seeing Q-Code errors.  After some trial and error, I got the machine to booth by installing only a single DIMM in the B2 slot.  If I install a 2nd DIMM in the A2 slot, I see an error code of 55.

I have seen others experience something similar and it seems like folks thinks that there is some issue either with the CPU install or the motherboard.  I have updated all the drivers, but I cannot get the machine to boot with 2 DIMMs; the boot up process take a while and I can see the Q-codes cycle through, but eventually it settles on code 55.  Any suggestion on what I could try would be appreciated!


Level 8

BTW, I have tried both DIMMs in the B2 slot and the PC boots, so the memory modules themselves are fine.  It is just that I cannot use both modules!

The memory speed is showing up as 4000MHz even though the memory is rated at 5200MHz.  Note that the i9 CPU I have is 12th gen.

Thx for the links.  I do see that the 12th gen i9 won't get to max speed.  I should still be able to use 2 32 GB DIMMs.

Super Moderator

If A2 is totally unresponsive and results in 55 you should consider reseating the CPU. Check the pin pad for any debris or bent pins, then remount the cooler whilst ensuring for consistent mounting pressure. DIMM slot issues are often related to improper CPU pin pad contact.

13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090

I tried reseating the CPU, but A2 remains unresponsive.  I used some compressed air as well to clean out potential debris.  Anyway, I moved to another motherboard and also went with the 14th gen i9.  The system is up an running now!

Thx for all the help.