C5 code on B650D4U

Dai wrote: I just picked up a B650D4U to build a server with. When I turn it on, it doesn't fully POST. Looking at the Dr. Debug codes, I see 15 followered by C5 where it stops. Never get VGA output though it'll take the display out of low power mode, nothing ever comes up just black screen. The manual doesn't list C5, but says 15 is something like northbridge init.

C5 often seems to point toward a memory initialization or training issue, even if it's not clearly documented in the manual. I'd try booting with a single DIMM in the recommended slot, reseating both the CPU and memory, and, if possible, updating the BIOS using the board's flash feature before assuming there's a hardware fault.

It would also help to know which CPU and RAM kit you're using, since some early BIOS versions had compatibility issues with certain DDR5 modules.


Edited by Xaltar - 29 Jun 2026 at 4:59am

Where do you contact them to get support?

Is there a change to post it here so i can grab it ?

reach out to support to get a beta version of the bios, that fixed it for us.

I'm surprised you are having the issue with a 4004/7000 cpu, I thought it was due to the new gen 4005/9000 cpu.

We have 5 new B650D4U boards 2 from vendor A, 3 from vendor B. Vendor B boards have this C5 issue after upgrading bios to 20.05 in order to support Epyc 4005/Ryzen 9000.
Swapping the memory from from a functioning A board to B boards, the issue appears inherent to the batch of B boards.


If anyone has resolution/other on this, it would be appreciated.