Question PC frozen with “AA” MB code after POST

[timmyw]

Hi everyone,

I’m experiencing some issues with my PC, and I’d appreciate any help or advice. Here’s what’s happening:

1. The system POSTS successfully with a single beep.
2. After POST, it hangs when trying to boot into either Windows 11 or Ubuntu—Windows freezes at the splash screen, and Ubuntu shows a black screen.
3. The motherboard error code remains static at "AA."
4. It also freezes when trying to boot from USB devices (e.g., Windows Bootable USB stick, Hiren's Boot USB).
5. Both the mouse and keyboard become unresponsive.
6. The temperature and power supply readings in BIOS appear normal.

System Specs:

• CPU: AMD ThreadRipper 3970X
• Motherboard: Gigabyte TRX40 Designare Rev 1.0
• RAM: 256GB
• GPU: 2x RTX 3090
• PSU: Corsair AX1600i

What I’ve tried so far:

1. Tested RAM modules one by one.
2. Re-seated the GPUs.
3. Removed and tested SSDs individually.
4. Update BIOS to be the latest
5. Cleared CMOS and reset the BIOS.
6. Checked the PSU—everything appears normal with a green status light.

Unfortunately, none of these steps have resolved the issue. Has anyone encountered something similar or have any suggestions on what to try next?


Thank you!

 

[COLGeek]

If you remove one GPU and start the system, does it make any difference?

 

[kerberos_20]

AA code doesnt mean anything wrong going on
AA - System has transitioned into ACPI mode. Interrupt controller is in APIC mode
that means system is running as it should and is in or about to go into OS (bios leaving control to OS)

are you able to run memtest?
if not, try reseating CPU

 

[timmyw]

Thanks COLGeek and kerberos_20, yes I have tried removed one GPU, still having the same issue.
I have also done the memtest, no error found.

I will try reseating the CPU

 

[timmyw]

Hi everyone,

In addition to the previous steps, I've done the following tests, but the issue persists:

1. Tested the PC with a different PSU, using only one RAM module and one GPU (as Threadripper has no integrated GPU).
2. Re-seated the CPU and inspected the socket—no bent pins found.
3. Removed all RAM and powered on; motherboard displayed code "10" with no beep, and the DRAM indicator light was on.
4. Scanned the system SSD—no errors found.
5. Attempted to boot from USB devices (Windows 11 and Hiren’s Boot) again; system still hangs at motherboard code "AA."
6. Tried entering Ubuntu recovery mode, but it got stuck, and the motherboard code remained "AA."

Are there any other tests I can try? I'm struggling to pinpoint which component might be causing the issue.

 

[kerberos_20]

that linux window shows usual efi messages from secure boot or measured boot being enabled
so disable/reset tpm and disable/reset secureboot

this is being printed to uefi text console, after this it should be printing to GPU framebuffer console, which would suggest kernel driver incompatibility with your GPU?

can you try disable uefi mode (enable csm and set storage to legacy)

 

[timmyw]

that linux window shows usual efi messages from secure boot or measured boot being enabled
so disable/reset tpm and disable/reset secureboot

this is being printed to uefi text console, after this it should be printing to GPU framebuffer console, which would suggest kernel driver incompatibility with your GPU?

can you try disable uefi mode (enable csm and set storage to legacy)

Thanks. I have disabled both Secure Boot and TPM. Enable CSM and set storage to legacy only. Issue still persist..

 

[timmyw]

that linux window shows usual efi messages from secure boot or measured boot being enabled
so disable/reset tpm and disable/reset secureboot

this is being printed to uefi text console, after this it should be printing to GPU framebuffer console, which would suggest kernel driver incompatibility with your GPU?

can you try disable uefi mode (enable csm and set storage to legacy)

The issue is not related to Ubuntu only, but the system was struggled to boot into USB bootable devices, whether it is Ubuntu or WIndows 11.

 

[timmyw]

Just checking if there is any answers for this question as I am still experiencing the issue.