I have a friend who's just starting out with Arch, and I've been getting him started on his install. His system uses a Biostar 6100-939 motherboard and an Athlon64 processor.
Everything has been working so far except sound. According to documentation, the correct ALSA driver for his nForce4 chipset should be the snd_intel8x0 module. However, loading this module didn't make any soundcards available to alsamixer.
We started to investigate the problem, and recently found this: http://jrbelvin.freeshell.org/weblog/linux/mcp51-alsa stating that the problem is fixed with the 1.0.11rc3 release of ALSA. We also found this : http://www.nvnews.net/vbulletin/showthread.php?t=60493 covering the same issue. We tried applying the patch listed in that forum to a build of the ArchCK kernel. While we were able to confirm that our patch really did patch the kernel, and that the patched kernel built, the snd_intel8x0 module still didn't work when we loaded our patched kernel.
So now it seems like we'll have to properly use the 1.0.11rc3 release of ALSA to get sound working on his computer until 1.0.11 is finalized and merged into the kernel. Does anyone have any experience on patching a kernel to use a different release of ALSA? Any help would be appreciated.
I had the same problem with my new computer (less than a week old) using an ASRock K8NF4G-SATA2 board. For me the problem stopped when I switched to the 2.6.16 kernel then in testing but now in current. If it's not working with that kernel try modprobing snd-intel8x0 by hand and running alsaconf.
I actually made packages of alsa-lib and alsa-driver 1.0.11rc4 for myself in the process, but I've switched away from those again, so I don't think they should be needed for NF4/MCP51 to work. That said if your problem doesn't go away I'll be happy to post the PKGBUILDs I modified or even send the packages themselves (with absolutely no guarantees).