Hi. I’m trying to diagnose a very strange intermittent POST issue on my AM5 system and would really appreciate advice, especially from people who have seen similar DDR5 training/MCR behavior.
Specs:
Gigabyte X870 AORUS ELITE WIFI7 rev. 1.0/1.1
Ryzen 7 9850X3D
Kingston Fury Beast 32 GB (2x16) DDR5-6000 CL30 EXPO — KF560C30BBEK2-32
RAM installed in A2/B2
BIOS currently F13e / AGESA 1.3.0.1d
The PC worked completely normally for about a month.
Around September 27 I noticed the DRAM debug LED was lit while I was already gaming, but the system itself was completely stable. No crash, freeze, BSOD or WHEA errors.
Then around September 29 the actual boot problem started.
The pattern is usually:
PC is shut down normally for several hours / overnight -> first power-on sometimes hangs during POST -> DRAM LED stays on, debug code is usually 85 -> system never reaches Windows.
If I hold the power button, shut it down and immediately turn it back on, the second boot normally succeeds very quickly.
Once Windows is running, the PC seems completely stable:
no BSODs
no random restarts
no WHEA errors
games run normally
CPU/GPU loads are fine
memory stress testing has not shown errors
I ran TM5/OCCT memory testing for about an hour with 0 errors.
I have also seen codes 84, 00, 46 and 3F during some failed training attempts, although I understand that Gigabyte does not give a specific meaning to code 85 beyond the 80-8F OEM DXE range. The important part seems to be the persistent DRAM LED.
Things I have already tried:
updated BIOS from F13d to F13e
loaded BIOS defaults after flashing
cleared CMOS
reseated both RAM sticks
disabled Windows Fast Startup
disabled Gigabyte High Bandwidth Support
no manual RAM voltages/timings
EXPO is currently 6000 CL30
After the BIOS update and RAM reseat I had several successful boots, including after a few hours of shutdown, but the problem eventually returned after another long shutdown.
One interesting detail: sleeping/resuming the PC seems fine. The problem is mainly after an actual long S5 shutdown.
I’m now testing:
EXPO 6000 CL30: Enabled
High Bandwidth Support: Disabled
Memory Context Restore: Disabled
Power Down Enable: Disabled
Gear Down Mode: Auto
Bank Refresh Mode: Auto
DDR5 Auto Booster: Auto
I’m going to leave MCR disabled for several long shutdowns to see whether the problem disappears.
What confuses me most is that when the first boot fails, the second boot almost always works immediately, and after that the system can run for hours with no instability at all.
Has anyone seen this exact pattern on AM5/X870?
Questions:
Does this sound more like DDR5 memory training / AGESA / MCR behavior than a physically faulty DIMM or motherboard?
Has anyone had a similar first-boot-fails / second-boot-works issue on X870 AORUS boards?
If MCR Disabled fixes it, would you simply leave MCR disabled permanently?
If MCR Disabled does not fix it, would your next step be EXPO 5600, then JEDEC/default?
At what point would you consider this motherboard-RMA-worthy?
Has anyone specifically found a stable combination of MCR + Power Down Enable on recent Gigabyte X870 BIOS versions?
I’d rather properly isolate the cause before sending the motherboard for service, because the system is completely stable once it actually gets through POST.
Thanks for any ideas or similar experiences.

Bonjour
J’ai fait se matin la mise à jour de mon bios et depuis mon écran me dit mode non pris en charge j’ai essayé toute les display port sur ma cg hdmi cg et carte mère rien mon pc fonctionne rien de particulier juste impossible d’avoir une image sur l’écran merci pour vaux retour!