ASROCK B660M Steel Legend Manual page 20

2.4 Expansion Slots (PCIe Slots)
There are 3 PCIe slots on the motherboard.
Before installing an expansion card, please make sure that the power supply is
switched off or the power cord is unplugged. Please read the documentation of the
expansion card and make necessary hardware settings for the card before you start
the installation.
PCIe slots:
PCIE1 (PCIe 5.0 x16 slot) is used for PCIe x16 lane width graphics cards.
PCIE2 (PCIe 3.0 x1 slot) is used for PCIe x1 lane width cards.
PCIE3 (PCIe 3.0 x1 slot) is used for PCIe x1 lane width cards.
B660M Steel Legend
17