MSI B760M Mortar Second GPU Slot | Generated by AI
Question: How to use the second GPU slot on MSI MAG B760M Mortar WiFi when the lower PCIe slot is blocked by an adapter/cable?
Answer:
Your motherboard technically has two PCIe slots, but the physical layout is the limitation.
MSI MAG B760M Mortar WiFi DDR5 layout:
CPU
|
| PCIe x16 (top slot)
| =======================
| GPU (RTX 4070 / MI50)
|
| M.2 / chipset area
|
| PCIe x16 physical (bottom slot, x4 electrical)
| =======================
|
| PCI cards / adapters
The problem is usually:
- Your first GPU is 2-3 slot thick
- MI50 is a server blower card, often ~2 slots
- The lower PCIe slot is very close
- M.2 adapter / USB adapter / capture card / cable blocks airflow or physical insertion
This is a common mATX problem.
Solutions:
Option 1 — PCIe riser cable (best solution)
Use a PCIe x16 riser:
Motherboard bottom PCIe slot
|
|
PCIe riser cable
|
|
GPU mounted vertically
Example:
[CPU]
|
[RTX 4070]
|
-----------------
bottom PCIe
|
riser
|
MI50 outside case
For AI workloads this is fine because the bottom slot is only PCIe 4.0 x4 anyway. You are not doing gaming SLI.
For LLM inference/training:
- GPU bandwidth matters less than VRAM capacity
- PCIe x4 is often acceptable
Option 2 — Move the adapter
If the adapter is:
- WiFi card
- USB expansion
- sound card
- NVMe PCIe adapter
move it.
Your motherboard already has:
- WiFi 6E
- multiple USB ports
- M.2 slots
You may not need the PCIe adapter.
Option 3 — Use a larger ATX motherboard
If your goal is:
RTX 4070
+
AMD MI50
+
maybe another GPU later
mATX is the wrong form factor.
A full ATX board gives:
GPU 1
(empty spacing)
GPU 2
(empty spacing)
GPU 3
Examples:
- Z790 ATX boards
- W790 workstation boards
Option 4 — Remove the case slot limitation
Sometimes the motherboard has space but the case bracket prevents the second GPU.
Check:
- number of expansion slots on the case
- GPU thickness
- PSU shroud blocking the bottom area
For your specific setup:
i9-13900KF
MSI B760M Mortar WiFi
RTX 4070
AMD MI50
I would do:
Top PCIe x16:
RTX 4070
Bottom PCIe x4:
PCIe riser cable
|
MI50 outside/vertical mount
This is actually a very normal AI workstation setup. The MI50 does not need PCIe x16 for most LLM experiments; the 16GB HBM2 memory is the valuable part.