I am wondering the same thing, documentation on nvidia, card manufacturers, sound card manufacturers are all slim. On top of that all the topics I have read on the net about it are the same.
Some people say no way, dvi cant do audio at all accept ATI?s use of the analog pins on DVI-I.
But I know that is not true because all nvidia card I have seen 7x/8x/9x have SPDIF pins (Even if not Advertised in specs). Ex. my EVGA 8800GTS G92 has SPDIF pins but no docs can be found that say that.
The DVI / HDMI audio Lack of standardization is sick and twisted.
And common card manufacturers how much bother and extra expense can it be to ad a 2-pin SPDIF cable. Some do bust most don?t. I think it is more that they don?t want to deal with the responsibility of supporting how to set it up.