MSI B450M-A PRO MAX II Manuel D'utilisation page 28

PCI_E1~2: PCIe Expansion Slots
⚠
Important
If you install a large and heavy graphics card, you need to use a tool such as MSI
∙
Graphics Card Bolster to support its weight to prevent deformation of the slot.
When adding or removing expansion cards, always turn off the power supply and
∙
unplug the power supply power cable from the power outlet. Read the expansion
card's documentation to check for any necessary additional hardware or software
changes.
PCI_E1: PCIe 3.0 x16 (From CPU)
PCI_E2: PCIe 2.0 x1 (From B450 chipset)
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