ASROCK X299 Steel Legend Handbuch Seite 20

2.4 Expansion Slots (PCI Express Slots)
There are 5 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 x4 lane width graphics cards.
PCIE3 (PCIe 3.0 x16 slot) is used for PCI Express x16 lane width graphics cards.
PCIE4 (PCIe 3.0 x1 slot) is used for PCI Express x1 lane width cards.
PCIE5 (PCIe 3.0 x16 slot) is used for PCI Express x8 lane width graphics cards.
* If you install CPU with 48 lanes, PCIE1/PCIE2/PCIE3/PCIE5 will run at x16/x4/
x16/x8.
* If you install CPU with 44 lanes, PCIE1/PCIE2/PCIE3/PCIE5 will run at x16/x4/
x16/x8.
* If you install CPU with 28 lanes, PCIE1/PCIE2/PCIE3/PCIE5 will run at x16/x4/
x8/x0.
PCIe Slot Configurations (For CPU with 48 PCIe lanes)
Single Graphics Card
Two Graphics Cards in
CrossFireX
Mode
Three Graphics Cards in
3-Way CrossFireX
or 3-Way SLI
18
PCIE1
x16
TM or SLI TM
x16
TM Mode
x16
TM
Mode
PCIE2 PCIE3 PCIE5
N/A N/A
N/A x16
N/A x16
N/A
N/A
x8