Motherboard DACs

[mansr]

The challenge with putting a DAC in the same metal case as the motherboard is avoiding interference from all the EM noise present there. Whether as a plug-in PCIe card (like the EVGA one) or on the main PCB doesn't really matter.

[mansr]

In a typical PC, one of the main chips includes a High Definition Audio (HDA) controller accessed over PCIe (PCI in older designs). There are also HDA controllers available as separate chips, also using PCIe, from e.g. Cmedia. The driver programming model is defined in the HDA specification. This part is somewhat analogous to the EHCI specification for USB controllers.

 

The HDA controller interfaces with an external codec (DAC and ADC) chip over an HDA link. This is a bidirectional synchronous serial interface carrying multiplexed command/response and data streams in a fixed-length frame structure. Comparing to the DAC chips we are familiar with, the HDA link combines the functionality of the I2C and I2S links commonly used.