PCIe Lane Bifurcation and Bandwidth Sharing on MSI X870E / X870 Motherboards
Motherboards
In a computer system, PCIe lanes are provided by both the processor and the chipset to support a wide range of components. To make more efficient use of these lanes and support various devices, motherboard manufacturers often design their boards to allow components such as PCIe slots, M.2 SSD slots, and USB4 ports to share PCIe bandwidth.
While this approach allows for greater flexibility, it can also introduce complexity and lead to confusion for some users. To help clarify this, we’ve compiled a detailed overview of the PCIe lane bifurcation and bandwidth sharing configurations on MSI X870E and X870 motherboards.
MEG X870E GODLIKE
PCIe / M.2 / USB4 Specifications and Lane Sharing Overview
Below is a detailed breakdown of each slot and port, including its connection, supported speed, and any shared bandwidth configurations.
Slot / Port
Connected to
Speed Supported
Shares Bandwidth With
PCI_E1
CPU
Up to PCIe 5.0 x16
PCI_E2
PCI_E2
CPU
Up to PCIe 5.0 x8
PCI_E1
PCI_E3
Chipset
Up to PCIe 4.0 x4
M2_4
USB4
CPU
Up to PCIe 5.0 x4
M2_2
M2_1
CPU
Up to PCIe 5.0 x4
No
M2_2
CPU
Up to PCIe 5.0 x4
USB4
M2_3
Chipset
Up to PCIe 4.0 x4
No
M2_4
Chipset
Up to PCIe 4.0 x2
PCI_E3
M2_5
Chipset
Up to PCIe 4.0 x4
No
PCIe Lane Sharing Notes:
- PCI_E1 and PCI_E2 share the CPU's PCIe 5.0 x16 lanes.
- PCI_E3 and M2_4 share the chipset’s PCIe 4.0 x4 lanes.
- M2_2 and rear USB4 ports share the CPU’s PCIe 5.0 x4 lanes.
Supported PCIe Lane Bifurcation in BIOS
You can configure PCIe lane bifurcation settings in the BIOS.
Slot
Bifurcation
PCI_E1 (CPU)
x16, or x8+x8, or x8+x4+x4, or x4+x4+x4+x4
MPG X870E CARBON WIFI
PCIe / M.2 / USB4 Specifications and Lane Sharing Overview
Slot / Port
Connected to
Speed Supported
Shares Bandwidth With
PCI_E1
CPU
Up to PCIe 5.0 x16
PCI_E2 & M2_2
PCI_E2
CPU
Up to PCIe 5.0 x4
PCI_E1 & M2_2
PCI_E3
Chipset
Up to PCIe 4.0 x4
No
USB4
CPU
Up to PCIe 5.0 x4
No
M2_1
CPU
Up to PCIe 5.0 x4
No
M2_2
CPU
Up to PCIe 5.0 x4
PCI_E1 & PCI_E2
M2_3
Chipset
Up to PCIe 4.0 x4
No
M2_4
Chipset
Up to PCIe 4.0 x4
No
PCIe Lane Sharing Notes:
- PCI_E1, PCI_E2 and M2_2 share the CPU's PCIe 5.0 x16 lanes.
Slot
Bifurcation
PCI_E1 (CPU)
x16, or x8+x8, or x8+x4+x4, or x4+x4+x4+x4
MAG X870E TOMAHAWK WIFI
PCIe / M.2 / USB4 Specifications and Lane Sharing Overview
Slot / Port
Connected to
Speed Supported
Shares Bandwidth With
PCI_E1
CPU
Up to PCIe 5.0 x16
No
PCI_E2
Chipset
Up to PCIe 3.0 x1
No
PCI_E3
Chipset
Up to PCIe 4.0 x4
No
USB4
CPU
Up to PCIe 5.0 x4
M2_2
M2_1
CPU
Up to PCIe 5.0 x4
No
M2_2
CPU
Up to PCIe 5.0 x4
USB4
M2_3
Chipset
Up to PCIe 4.0 x4
No
M2_4
Chipset
Up to PCIe 4.0 x4
No
PCIe Lane Sharing Notes:
- M2_2 and Rear USB4 share the CPU's PCIe 5.0 x4 lanes.
Slot
Bifurcation
PCI_E1 (CPU)
x16, or x8+x8, or x8+x4+x4, or x4+x4+x4+x4
MAG X870 TOMAHAWK WIFI
PCIe / M.2 / USB4 Specifications and Lane Sharing Overview
Slot / Port
Connected to
Speed Supported
Shares Bandwidth With
PCI_E1
CPU
Up to PCIe 5.0 x16
No
PCI_E2
Chipset
Up to PCIe 3.0 x1
No
PCI_E3
Chipset
Up to PCIe 4.0 x4
M2_3
USB4
CPU
Up to PCIe 5.0 x4
M2_2
M2_1
CPU
Up to PCIe 5.0 x4
No
M2_2
CPU
Up to PCIe 5.0 x4
USB4
M2_3
Chipset
Up to PCIe 4.0 x2
PCI_E3
M2_4
Chipset
Up to PCIe 4.0 x4
No
PCIe Lane Sharing Notes:
- M2_2 and Rear USB4 share the CPU's PCIe 5.0 x4 lanes.
- PCE_E3 and M2_3 share the chipset's PCIe 4.0 x4 lanes.
Supported PCIe Lane Bifurcation in BIOS
Slot
Bifurcation
PCI_E1 (CPU)
x16, or x8+x8, or x8+x4+x4, or x4+x4+x4+x4
X870E GAMING PLUS WIFI
PCIe / M.2 / USB4 Specifications and Lane Sharing Overview
Slot / Port
Connected to
Speed Supported
Shares Bandwidth With
PCI_E1
CPU
Up to PCIe 5.0 x16
No
PCI_E2
Chipset
Up to PCIe 3.0 x1
No
PCI_E3
Chipset
Up to PCIe 4.0 x4
No
PCI_E4
Chipset
Up to PCIe 3.0 x1
No
USB4
CPU
Up to PCIe 5.0 x4
No
M2_1
CPU
Up to PCIe 5.0 x4
No
M2_2
Chipset
Up to PCIe 4.0 x4
No
M2_3
Chipset
Up to PCIe 4.0 x4
No
Supported PCIe Lane Bifurcation in BIOS
Slot
Bifurcation
PCI_E1 (CPU)
x16, or x8+x8, or x8+x4+x4, or x4+x4+x4+x4
X870 GAMING PLUS WIFI
PCIe / M.2 / USB4 Specifications and Lane Sharing Overview
Slot / Port
Connected to
Speed Supported
Shares Bandwidth With
PCI_E1
CPU
Up to PCIe 5.0 x16
No
PCI_E2
Chipset
Up to PCIe 3.0 x1
No
PCI_E3
Chipset
Up to PCIe 3.0 x1
No
PCI_E4
Chipset
Up to PCIe 4.0 x4
M2_3
USB4
CPU
Up to PCIe 5.0 x4
No
M2_1
CPU
Up to PCIe 5.0 x4
No
M2_2
Chipset
Up to PCIe 4.0 x4
No
M2_3
Chipset
Up to PCIe 4.0 x2
PCI_E4
PCIe Lane Sharing Notes:
- PCI_E4 and M2_3 share the chipset’s PCIe 4.0 x4 lanes.
Supported PCIe Lane Bifurcation in BIOS
Slot
Bifurcation
PCI_E1 (CPU)
x16, or x8+x8, or x8+x4+x4, or x4+x4+x4+x4
PRO X870E-P WIFI
PCIe / M.2 / USB4 Specifications and Lane Sharing Overview
Slot / Port
Connected to
Speed Supported
Shares Bandwidth With
PCI_E1
CPU
Up to PCIe 5.0 x16
No
PCI_E2
Chipset
Up to PCIe 3.0 x1
No
PCI_E3
Chipset
Up to PCIe 4.0 x4
No
PCI_E4
Chipset
Up to PCIe 3.0 x1
No
USB4
CPU
Up to PCIe 5.0 x4
No
M2_1
CPU
Up to PCIe 5.0 x4
No
M2_2
Chipset
Up to PCIe 4.0 x4
No
M2_3
Chipset
Up to PCIe 4.0 x4
No
Supported PCIe Lane Bifurcation in BIOS
Slot
Bifurcation
PCI_E1 (CPU)
x16, or x8+x8, or x8+x4+x4, or x4+x4+x4+x4
PRO X870-P WIFI
PCIe / M.2 / USB4 Specifications and Lane Sharing Overview
Slot / Port
Connected to
Speed Supported
Shares Bandwidth With
PCI_E1
CPU
Up to PCIe 5.0 x16
No
PCI_E2
Chipset
Up to PCIe 3.0 x1
No
PCI_E3
Chipset
Up to PCIe 3.0 x1
No
PCI_E4
Chipset
Up to PCIe 4.0 x4
M2_3
USB4
CPU
Up to PCIe 5.0 x4
No
M2_1
CPU
Up to PCIe 5.0 x4
No
M2_2
Chipset
Up to PCIe 4.0 x4
No
M2_3
Chipset
Up to PCIe 4.0 x2
PCI_E4
PCIe Lane Sharing Notes:
- PCI_E4 and M2_3 share the chipset’s PCIe 4.0 x4 lanes.
Supported PCIe Lane Bifurcation in BIOS
Slot
Bifurcation
PCI_E1 (CPU)
x16, or x8+x8, or x8+x4+x4, or x4+x4+x4+x4
Note:
The configurations above apply when using AMD Ryzen 7000 and Ryzen 9000 series processors. For limitations regarding Ryzen 8000 Series processors, please refer to the specific motherboard product webpage
.
MSI X870E/X870/B850/B840 Gaming Motherboards: https://us.msi.com/Landing/amd-am5-x870e-x870-b850-b840-ryzen-9000-x3d-best-ai-gaming-motherboard
