with pulse, it's silent; without sound works

It should perhaps also be mentioned that "codec" is a specific bit of jargon specific to the HDA spec (available on the intarwebs; this is how I know about these things, although it's been a while and I'd greatly appreciate supplements/corrections where appropriate).

The HDA spec has a tree structure, and one of the nodes is a "codec," referring to a virtualized interface to a block that Does Stuff. This is used to interesting effect with the sound card discussed at http://blogs.amd.com/home/2009/06/16/turning-it-up-to-11/, where the HDA protocol itself is used as a transport/formalization of a higher-level protocol used to drive a particularly novel consumer-level sound card.

IIRC. It's been a bit since I read the specs on this card and therefore also the HDA specs to understand Intel HDA as it was being used here. (Sadly, I never got enough hand-holding to get a driver up and running on ALSA and perhaps also lacked the motivation, not actually having hardware to play/test with.)