Originally Posted by Nagorak
My C6H works. Only problem is if I overclock my memory too high I get a C5 error on a cold boot. I have to clear the bios every time I cold boot and then restore from my saved profiles. Annoying, but manageable.
My C7H 3700x was also getting that C5 error on a cold boot. Clear bios/restore saved profile, bleh. Then I found this magical (new?) setting in the Version 2501 bios under Extreme Tweaker\External Digi+Power Control. It's at the -very- bottom of that section on the C7H and it's called "Dram VBoot Voltage".
So, by setting that to the v my mem requires in addition to the regular dram voltage setting I haven't seen the C5 error since. Is that one the setting you tried that didn't work?
If not, then maybe the new bios Version 7201 dated 2019/07/18
for the C6H has it too? Version 7106 2019/07/05 was the previous one.