ok lets take PCM then, to summarise my simplistic view, nowadays windows generates PCM 'packets' using your system ressources and sends them to an audio output, using pcie, usb, etc. What the sound card only does is convert the pcm signal to analogue waves correct? That means that all the 3D positioning and filters of the game's sound is done by the main cpu and that the quality of the sound card has zero impact on the number of fps you get?
That is not entirely accurate. You are forgetting the number of interrupts involved in all of that. Each interrupt causes a context switch. Interrupts is what a good sound card saves you. That is where the gains are made. In the end, all sound is simply converted from digital to analog, regardless of the bus.
Before it gets to that conversion is where CPU savings can be made. The dumbest sound device is simply an A/D converter with the CPU doing all the heavy lifting. The smartest sound device just needs parameters filled out and it takes care of the sound work, including positioning.
For instance, we say we need this stream, played at a specific level, over a specific channel, at this sample rate, at this bit depth and hand the sound driver a raw sound packet. After that, the division of labor depends on the intelligence of the sound device as to how much is done in the driver.
Does this mean you will get a significant boost in frame rate? Probably not. It does not mean there is nothing to be gained from an intelligent sound card. For example, you have no idea if a sound is not played due to the limitations of the hardware.
