ASROCK X399M Taichi Manual page 25

2.4 Expansion Slots (PCI Express Slots)
There are 3 PCI Express 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 3.0 x16 slot) is used for PCI Express x16 lane width graphics cards.
PCIE2 (PCIe 3.0 x16 slot) is used for PCI Express x16 lane width graphics cards.
PCIE3 (PCIe 3.0 x16 slot) is used for PCI Express x16 lane width graphics cards.
PCIe Slot Configurations
Single Graphics Card
Two Graphics Cards in
CrossFireX
Mode
For a better thermal environment, please connect a chassis fan to the motherboard's
chassis fan connector (CHA_FAN1 or CHA_FAN2 ) when using multiple graphics
cards.
22
PCIE1
x16
x16
TM TM
or SLI
x16
PCIE2 PCIE3
N/A N/A
x16 N/A
N/A x16