B550 taichi Intermittent booting issue code 15

# B550 taichi Intermittent booting issue post code 15

## tldr

I am looking for guidance and resources on troubleshooting a motherboard/ram/cpu/config issue.
I am of the opinion that my issue is not unique as I have been able to repeat it with different hardware.
I believe others have encountered this problem in the wild and I would like to know what your results and outcomes were. I don't think the typical troubleshooting is appropriate here (clear CMOS, update bios, reseat cpu/ram, etc).


Relevant hardware 1:

- Model Name: B550 Taichi
- BIOS Version: 2.00 (latest as of 2022-01)
- Purchase Date: late, 2020
- CPU: Ryzen 9 3900XT 12-core, 24-Threads
- Memory: KVR32N22D8/32 x 2 (slot A2/B2)
- Video Card: Radeon 6800,PCIe (top slot)

Relevant hardware 2:

- Model Name: B550 Taichi razer edition
- BIOS Version: 1.60 (latest as of 2022-01)
- Purchase Date: Jan, 2022
- CPU: Ryzen 9 3900XT 12-core, 24-Threads
- Memory: KVR32N22D8/32 x 2 (slot A2/B2)
- Video Card: Radeon 6800,PCIe (top slot)

Other Devices:
Default bios config. No overclocking.

## Symptoms

- When booting (cold boot and ACPI restarts) the board fails to post
- In this state the board hex display readout shows code: 15 (Dr Debug code)
- In order to get the system to boot, the chassis or on-board rest button must be pressed, wait for the readout to reach code 15, after ~ 8 seconds if it has not continued past code 15 then press reset again. This needs to be repeated up to 10 times in order to get it to go past code 15
- Once it is able to get past code 15 then the system behaves normally.
- Removing one stick of RAM and booting only with a stick in slot A2 appears to remedy the problem.
- This is true with either stick of RAM. Memtest was run against these sticks, see **Details** section below


## Resources

- 3900XT (Matisse 2)
- [B550 Taichi CPU QVL](https://www.asrock.com/mb/AMD/B550%20Taichi/#CPU)
- [B550 Taichi Razer CPU QVL](https://www.asrock.com/mb/AMD/B550%20Taichi%20Razer%20Edition/Specification.asp#CPU)
- [B550 Taichi Matisse Memory QVL](https://www.asrock.com/mb/AMD/B550%20Taichi/#MemoryMS)
- [B550 Taichi Razer Matisse QVL](https://www.asrock.com/mb/AMD/B550%20Taichi%20Razer%20Edition/Specification.asp#MemoryMS)
- [KVR32N22D8/32](https://www.kingston.com/dataSheets/KVR32N22D8_32.pdf) is identified in both QVLs and slotted in the appropriate slot according to the manual (A2/B2)
- [B550 Taichi Manual](https://download.asrock.com/Manual/B550%20Taichi.pdf)
- Relevant section on memory: 2.3, page 23
- [B550 Taichi Razer Manual](https://download.asrock.com/Manual/B550%20Taichi%20Razer%20Edition.pdf)
- Relevant section on memory: 2.3, page 24
- [Official Technical support page](https://event.asrock.com/tsd.asp)
- A ticket was filed. Given all the information you see here the support rep responded with the following and nothing else.

```text
If you have 2 memory only, insert ont A2/B2 DIMM slots.
```
- [ASRock's general Dr Debug information page](https://www.asrock.com/support/faq.asp?id=334)
- The relevant section says the following.

```text
01 - 54 (except 0d), 5A- 60
Problem related to memory. Please re-install the CPU and memory then clear CMOS. If the problem still exists, please install only one memory module or try using other memory modules.
```

- [memtest86 v5.31b](https://www.memtest.org/)

## Details.

I have two motherboards

- B550 Taichi, purchased late 2020
- B550 Taichi Razer Edition, purchased Jan 2022

I had planned to RMA the first motherboard but after being faced with the prospect of being without my main workstation for an unknown period, I decided to take the more expensive route and buy a new-identical motherboard (as close as I could get).

I migrating the bare-minimum hardware (cpu, gpu, ram) over to the new system and updated the bios to the latest version.
Even with the default settings, this new motherboard experienced the exact same failure as described in the Symptoms section above.
*Post code 15 on the "Dr. debug" LED readout.*
*The system hangs intermittently on this state.*

Okay so this seems to suggest there is a problem with one of the following.

- The motherboard config
- The CPU
- The RAM

I tested each RAM stick in individually [memtest86 v5.31b](https://www.memtest.org/)
Each stick passed the test with one full run taking approximately ~ 1 hour 30 minutes to complete.
I want to let this test run longer but it'll have to wait until the weekend as I need my pc during the work-week.

I would appreciate any advice. Thank you.

- ButterSmuggler

P.S. As a matter of due-diligence I am posting this in the ASRock forums and the Level1Techs forums.