Troubleshooting Boot Failures When Combining GPU and High-Speed NIC on MSI B550 Tomahawk MAX WiFi Motherboard
Building a reliable Unraid server often involves integrating multiple high-performance components. However, compatibility issues can emerge, especially when using certain hardware configurations. In this article, we explore a common challenge faced by enthusiasts: boot failures when combining a GPU and a 10G network interface card (NIC) on a MSI B550 Tomahawk MAX WiFi motherboard.
System Overview
Before diving into the issue, here’s a summary of the hardware configuration involved:
- Processor: AMD Ryzen 9 3900X
- Motherboard: MSI MAG B550 Tomahawk MAX WiFi (latest BIOS installed)
- Memory: 32GB DDR4 RAM
- Graphics Card: NVIDIA GTX 970
- Network Interface Card: PCIe x8 Intel 10G NIC (installed in second x16 slot)
- Case: Fractal Define 7 XL
- Power Supply: Corsair RM1000e (modular)
- Operating System: Unraid
The Core Issue
The system boots normally with only the GTX 970 installed in the primary PCIe slot (PCI_E1). However, adding the 10G NIC to the second x16 slot (PCI_E3) results in the motherboard failing to POST, indicated by a persistent VGA red LED. Removing the NIC allows the system to boot normally. Notably, the small x1 slot (PCI_E4) cannot accommodate the NIC due to physical size constraints.
Troubleshooting Steps Attempted
Several configurations and BIOS settings were tested to resolve the issue:
- Forcing PCIe Gen3 mode instead of Auto
- Enabling “Above 4G Decoding” in BIOS
- Disabling Resizable BAR
- Toggling Compatibility Support Module (CSM) on and off
- Updating the motherboard BIOS to the latest version
- Verifying proper seating and power connections
- Testing with only the NIC installed (GPU removed), which successfully POSTs, indicating the NIC functions properly
Observations and Hypotheses
The persistent boot failure when both the GPU and the 10G NIC are installed suggests a possible lane allocation or compatibility issue within the B550 chipset. Specifically, it may be that the PCIe lanes managed by the chipset do not support simultaneous full x4 bandwidth for the NIC alongside the GPU on this motherboard model. This could be due to limitations inherent to the B
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