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!

 

[Colif]

if you get a BSOD during the installation process, its only going to be ram or processor or MB. Nothing else is in action until a later step in the install process

Try running memtest86 on each of your ram sticks, one stick at a time, up to 4 passes. Only error count you want is 0, any higher could be cause of the BSOD. Remove/replace ram sticks with errors. Memtest is created as a bootable USB so that you don’t need windows to run it

turn xmp off during the install and see if you can get past where you are.

Is ram on QVL of the motherboard? Did patriot test it with board?

Storage:not in

Its really hard to install windows if you don't have any storage in the PC - where is it meant to install it exactly?

I assume it was at one stage - Might need to wipe the ssd if its got a partial install of windows on it now - I can't tell since I don't know when it failed.

memory controller is on the CPU, could explain light maybe.

only real way to test a Ryzen CPU is to run Prime95 and see if it crashes. The results should show in a text file in the install folder for prime, from memory

instructions may be old, its a while since I used them:
Prime 95 Bootable - https://www.infopackets.com/news/10113/how-fix-bootable-prime95-stress-test-hardware
Prime 95 Instructions - https://appuals.com/how-to-run-a-cpu-stress-test-using-prime95/