I was able to get sound working on the new iMac by adding the following to alsa-driver-1.0.19/alsa-kernel/pci/hda/patch_realtek.c

case 0x106b4900: /* iMac 9,1 */

underneath line 7013 case 0x106b1000: /* iMac 24 */

(this kept it from using the alc883 since the revision_id is 0x100103).

I did find though, that using the mbp3 option is what allowed sound to work. The same issues with the macbook pro aluminum apply here. the channel must be switched to 2ch to mute built-in speakers and to 6ch to unmute. There is another issue here though. the playback from the speakers is barely audible, i'm guessing it's similar to the issue with the right speaker on the macbook pro. I'm guessing there needs to be adjustments to the pins defined.

My current alsa-info resides at http://www.alsa-project.org/db/?f=5bfaadf03f7134e9ef2c3a934fb4084d36ba2d93

If there's anything else I can do to help this along, let me know. I do have the macbook pro aluminum, so I can test there as well.

-Micah