Question Z690 Aorus Xtreme Waterforce boot issue, could it be RAM ?

[Gypsy_Tzar]

Greetings,

Building a new PC and I can't seem to get to the BIOS. Here is the config:
MB: Z690 Aorus Xtreme Waterforce
CPU: i9-12900KS
GPU: Auros Xtreme RTX 3090 Ti AOI
HDD: (2x) FireCuda 530 4TB PCIe NVMe SSD
RAM: 64 GB (4 x 16) G. Skill DDR5 z5 Trident (6400) (XMP 3.0)
PSU: ThermalTake ToughPower iRGB Plus 1250W

Steps taken so far:

• Have re-seated RAM
• Checked and re-seated all power
• Cleared CMOS
• Q-Flashed BIOS to F6d (but can't verify because can't get to the boot screen)

Problem: MB codes that come up are C2-C4-12-28-54-03-00. 54 leads me to think its RAM issue. And of course there were no indications of issues BEFORE I set up the custom water loop and locked everything in; fans and pump working correctly.

Thoughts: May have been too excited about getting 6400 DDR5 G. Skill RAM, I don't see it specifically on the list even though there are other lower speed G.Skills. I thought XMP might take care of this since I believe the RAM sticks natively run at 4800.

Just in case, I have ordered 32 GB (2x16) Aorus 4800 RAM to test and am waiting for Mr. Amazon to show up.

Thoughts and ideas?

Thanks in advance.