MSI PRO B550M-P GEN3 Manuel D'utilisation page 39

Onboard LEDs
EZ Debug LED
These LEDs indicate the debug status of the motherboard.
CPU - indicates CPU is not detected or fail.
DRAM - indicates DRAM is not detected or fail.
VGA - indicates GPU is not detected or fail.
BOOT - indicates the booting device is not detected
or fail.
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