: Ensure you have the Windows 10 64-bit version of the CMI8738 driver.

When you plug a CMI8738-based card into a modern motherboard, Windows might detect it as a "High Definition Audio Device" but fail to output sound, or it may show up as an "Unknown Device." This is because the specific instruction sets for the CMI8738 are not natively included in the Windows 11 kernel.

requires using legacy Windows 10 or generic drivers, as there is no specific "Windows 11" release for this aging hardware. While the chip is legacy, Windows 11's core architecture still supports many Windows 10 drivers. Recommended Driver Versions For a 64-bit system, you should look for driver version 8.1.8.1746

"Download and Install Cmi8738 Driver for Windows 11 64 Bit: A Step-by-Step Guide"