I don't know, my motherboard is this one:
http://www.newegg.com/Product/Product.asp?Item=N82E16813131022Supposedly 24-bit 192khz audio capable with the onboard chip (I am only using the built-in sound at this point, much better than the previous built-in solution I had from a few years ago). I listened to my 24-bit recordings (44.1khz) that were by no means recorded with ideal levels (one show averaged about -19dB and the other -14.5dB), and I heard clear differences between the original 24-bit and resulting 16-bit files through a good pair of Sony headphones. The sound was overall "smoother" and less harsh. If nothing else, I know that if I was at -19dB and made a 16-bit recording, the end result would not have been nearly as good as it turned out as I unfortunately ended up that way occassionally when I used to tape with my NJB3 due to the terrible meters. This time, my problem was being overly conservative, as these were the 2nd and 3rd shows I had taped with the unit and I had possessed it for about a week and a half; these were important shows so I didn't want to clip, and I knew from posts here that 24-bit allows you to be more conservative with the levels to less adverse effects. The ending result was the best tapes I've ever done, YMMV of course.