Question CPU LED Stays On After Windows Installer BSOD — Ryzen 5 5600 on MSI B550-A PRO

[33P4BLO]

Hello everyone,

I’m experiencing a persistent issue with my newly built PC:
CPU: AMD Ryzen 5 5600
Motherboard: MSI B550-A PRO (BIOS updated via Flashback to latest version)
RAM: 2x8GB Patriot Viper 3600MHz cl17 (running at default 2133MHz, no XMP enabled)
Storage:not in
GPU: Gigabyte RX 6600 XT Gaming OC

Problem description:
The system boots up normally, CPU LED lights up briefly during POST, then VGA and Boot LEDs go off, and the PC proceeds to Windows Installer. During installation or after a Blue Screen of Death (BSOD) error in Windows Installer, the PC restarts but gets stuck with the CPU debug LED constantly lit and only the CPU fan spinning. The BSOD I get is Oxc00021a. No display output is received after this point, and the system does not proceed with POST again.

Removing RAM causes the RAM LED to light up as expected, confirming the motherboard detects missing RAM. BIOS correctly detects CPU with proper core count and frequency. PSU and cables verified, no bent CPU pins, thermal paste applied properly.

What we know:
BIOS is definitely updated correctly.

The CPU is detected fine by BIOS and POST completes initially, so it’s likely not dead but may have issues during warm reboot or initialization phase.

RAM is recognized but runs at a default low frequency with voltage around 1.19V, which might be borderline unstable for this kit.

The problem occurs reliably after a Windows installer BSOD or system restart.

Removing GPU shifts the LED to VGA, so GPU is detected and seems fine.

Both RAM sticks inserted individually into port A2 do not change anything.

Another motherboard didn't fix it either

Likely cause:
The CPU debug LED staying lit after restart strongly suggests a failure during POST caused by memory initialization instability or CPU initialization failure on warm reboot.

RAM voltage possibly too low for stable operation without XMP, but voltage change hasn’t been tried yet.

Could also be a rare CPU fault causing failure after initial cold boot but stable BIOS POST.

Windows installer and USB drive is definitely not a problem.


Any advice or similar experiences would be greatly appreciated!

Thanks!

 

[Lutfij]

Welcome to the forums, newcomer!

my newly built PC:
CPU: AMD Ryzen 5 5600
Motherboard: MSI B550-A PRO (BIOS updated via Flashback to latest version)
RAM: 2x8GB Patriot Viper 3600MHz cl17 (running at default 2133MHz, no XMP enabled)
Storage:not in
GPU: Gigabyte RX 6600 XT Gaming OC
Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. Please state the BIOS version for your motherboard at this moment of time instead of stating latest.

Where did you source the installer for the OS?

The problem occurs reliably after a Windows installer BSOD or system restart.
You state having no storage in the system, then what are you trying to install the OS onto?

 

[33P4BLO]

Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:

CPU: AMD Ryzen 5 5600
CPU cooler: Wraith Stealth
Motherboard: MSI B550-A PRO
Ram: 2x8GB PATRIOT Viper Steel 3600mhz cl17
SSD: Lexar NM790 1tb
GPU: Gigabyte RX 6600 XT GAMING OC
PSU: Zalman MegaMax 500W v2
Chassis: Krux Vako
OS: Windows 11 Pro
Monitor: KTC H24F8

include the age of the PSU apart from it's make and model. Please state the BIOS version for your motherboard at this moment of time instead of stating latest.

PSU info:
Model: ZM500-TXII
ATXV12 Ver2.31
I bought it 2 weeks ago.
BIOS is 7C56vAJ from 2025-05-12

Where did you source the installer for the OS?

I used media creation tool from microsoft, but using official ISO and rufus not worked either. BTW I tried different USB drives and mobo ports without any success.

The problem occurs reliably after a Windows installer BSOD or system restart.
You state having no storage in the system, then what are you trying to install the OS onto?

I had the same problem on my previous motherboard (Gigabyte's B550 Aorus Elite). I thought changing the mobo would help, but it didn't. I didn't insert an SSD drive for the test, because I was only interested in whether the installer itself would run correctly, and I don't need a drive for that.

 

[Lutfij]

Model: ZM500-TXII
https://docs.google.com/spreadsheet...pZRB6Xt6JWkc/edit?gid=931697732#gid=931697732
Category E...that is a horrible unit.

Edit;

PSU Tier List rev. 17.0g - Cultists Network

PSU Tier List will help you to choose the best PSU out of hundreds of models on the market. From budget to the highest end Power Supplies.

cultists.network

 

[33P4BLO]

Model: ZM500-TXII
https://docs.google.com/spreadsheet...pZRB6Xt6JWkc/edit?gid=931697732#gid=931697732
Category E...that is a horrible unit.

Edit;

PSU Tier List rev. 17.0g - Cultists Network

PSU Tier List will help you to choose the best PSU out of hundreds of models on the market. From budget to the highest end Power Supplies.

cultists.network

I tried another power supply from a friend (600 or 650W) and it made no difference.

 

[Lutfij]

I tried another power supply from a friend (600 or 650W) and it made no difference.
For the sake of relevance, what is the make and model of your PSU? How old was his unit and what did it power prior to you using it? To add, a PSU can't be two different wattages, it's either 600W or 650, so which is it?

 

[33P4BLO]

I tried another power supply from a friend (600 or 650W) and it made no difference.
For the sake of relevance, what is the make and model of your PSU? How old was his unit and what did it power prior to you using it? To add, a PSU can't be two different wattages, it's either 600W or 650, so which is it?

He has a pre-built, so he probably doesn't know. I mean, it was 600W or 650W, so more than enough for my setup.

 

[Lutfij]

He has a pre-built, so he probably doesn't know. I mean, it was 600W or 650W, so more than enough for my setup.

Honestly, that doesn't answer anything. Wattage isn't the only thing on a PSU you look at when buying into a unit. A PSU that's been taxed and is old will output less power than it did when brand new. If you got the PSU from a friend, didn't you look at the label on the sides of the PSU?

You've tried multiple installers, multiple USB drives, changed your motherboard, worked with a bad quality PSU and then an unknown make/model/quality PSU from a friend, you're left with the processor and storage drive. You might want to take them(the remaining parts excluding the trash PSU) to another platform and breadboard it to see if your processor is indeed DoA.