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4 DIMMS of "Corsair Dominator Platinum DDR5 64GB(32 x 2)" to work in a ROG Maximus Z790 hero ???

Level 8

Has anyone gotten 4 DIMMS of the memory mentioned above to work in the Maximus Z790 Hero???
Oddly enough I have gotten 2 DIMMS to work for a total of 64GB of RAM. However they are not in the slots recommended for using only 2 DIMMS. I am using  A1 and A2 slot. The recommended slots for 2 DIMMS is A2 and B2. When I try this configuration the machine will not boot and shows a 55 error code on the board.
Any help would be appreciated. 


Super Moderator


Do you still receive Q-Code 55 after clearing the UEFI with modules in A2 and B2? If so, this may indicate a CPU pin pad contact or CPU cooler torque issue. The system should be able to POST in this configuration assuming no memory overclocking is applied (XMP).

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

I'm sorry, kind of a newbie with this BIOS. How would I go about clearing the UEFI?
Thanks for the help.


Your board has a "Clear CMOS" button on the rear I/O shield which clears the UEFI BIOS configuration.  See the following FAQ:

[Motherboard/Desktop] How to restore BIOS setting?

After clearing CMOS, go into the UEFI BIOS setup and press F5 to "load optimised defaults".  After that, do not make any BIOS configuration changes unless absolutely necessary (e.g. to select the correct boot device or deal with secure boot type issues).

If the system boots ok on optimised defaults, you can try letting it run MemTest for a while to check the health of your DIMMs.  If all seems ok, try just running like that for a day or two.  You won't have any performance tuning, and memory will be at default JEDEC speeds (no XMP), but see if the system is stable like that.  Running on defaults lets you figure out whether you have a configuration/overclocking/tuning type problem or a hardware problem.  The difference in performance between defaults and tweaked usually isn't too extreme for normal systems.

A problem with the CPU and cooler mount is a common cause for only 1 of the 2 memory banks (A and B) to work, as Silent_Scone said above.

Lastly, check if your memory part number is on the Maximus Z790 Hero Memory QVL.  Be sure to select your CPU type at the top of the QVL, as compatibility varies for different CPU types.  Pay particular attention to the "socket support" column; "1,2" is 1 and 2 DIMM configs only, and "1,2,4" is up to 4 DIMMs.

Thanks @Murph_9000 and @Silent_Scone I will give your suggestions a try and see if that solves it.