Fail to detect the eGPU

The customer is trying to connect an external GPU (NVIDIA RTX 4060) to the A8 via the USB4 port. However, the current BIOS version lacks required options including PCIe Hotplug, Above 4G Decoding, Resizable BAR, USB4 PCIe Tunneling, as well as the Chipset / AMD PBS / PCI Subsystem menu. Without these settings, the eGPU cannot be initialized.

This assumption may not be caused by the BIOS. The inference that missing eGPU-dock related BIOS options leads to the undetected external graphics card is invalid. The USB4 port of this model has been verified for eGPU compatibility during development (all models equipped with USB4 ports undergo such testing), and the test results were normal.

Among the BIOS features mentioned by the customer, only Resizable BAR is disabled by default. All other options are enabled by default and require no manual configuration.

Common reasons why the system cannot detect the graphics card:

1. High probability: Compatibility issues. Different eGPU docks adopt vastly different Thunderbolt/USB4 bridge controllers, firmware versions and PCIe bridge implementations. Some docks work fine on Intel Thunderbolt platforms but may fail enumeration, suffer intermittent disconnections or fail to recognize the GPU when connected to AMD USB4 hosts.
2. Common issue: Non-compliant cable quality. You must use a genuine cable supporting 40Gbps USB4/Thunderbolt 3/4. Cables with only USB-C form factor but inadequate PCIe tunneling capability or poor signal integrity will not work. Direct connection with a short cable is recommended for testing.
3. Low probability: Abnormal firmware or power supply of the eGPU dock. The dock PSU, PCIe slot power delivery, auxiliary GPU power supply and boot timing can all affect initialization. Certain docks behave abnormally with specific NVIDIA GPUs due to differences in GPU standby/boot timing.

Resizable BAR can only be enabled on discrete graphics cards and is not supported by integrated graphics. Therefore, even if Resizable BAR is turned on in BIOS, it will not apply to the A8’s integrated GPU and will still show as disabled.

To view the Resizable BAR setting in BIOS, you need to unlock the advanced BIOS menu with a tool before the option becomes visible and configurable: Advanced ——> PCI Subsystem Settings ——> Re-sizable BAR Support