Suponiendo que tienes la bios al día, la última es la 0910, intenta hacer un reset a valores de fábrica. En el manual también encontré esto sobre la configuración de la gráfica en la bios:
Graphics Configuration
Primary Display [Auto]
Allows you to select a primary display from iGPU, PCIE, or PCI graphic devices, or
select SG for switchable GFX. Configuration options: [Auto] [iGPU] [PCIE] [PCI] <- Asegúrate que no está en pci, en el peor de los casos puedes ponerlo manualmente en pcie si el auto no funciona.
iGPU Memory [64M]
Allows you to set the iGPU memory size. Configuration options: [32M] [64M] [96M]
[128M] ~ [448M] [480M] [512M] [1024M]
Render Standby [Enabled]
Allows you to enable or disable Render Standby by internal graphics devices.
Configuration options: [Disabled] [Enabled]
iGPU Multi-Monitor [Enabled]
Allows you to enable or disable the Lucid Virtu support for both the integrated and
discrete graphics. The iGPU shared memory size will be fixed at 64MB. Configuration
options: [Disabled] [Enabled]
NB PCIe Configuration <- Esto en auto debería ir bien.
Allows you to configure the NB PCI Express settings.
PCIE x16_1 [Auto]
Allows you to set the PCIE x16_1 link speed. Configuration options: [Auto] [Gen1]
[Gen2] [Gen3]
PCIE x16_2 [Auto]
Allows you to set the PCIE x16_2 link speed. Configuration options: [Auto] [Gen1]
[Gen2] [Gen3]