DFI KT600-AL onboard sound fails on kernels newer than 2.6.3

I'm using a homebrew PC; the motherboard, a <a href="http://us.dfi.com.tw/Product/xx_product_spec_details_r_us.jsp?PRODUCT_ID=2520&CATEGORY_TYPE=MB&SITE=NA">DFI KT600-AL</a>, has onboard sound support.

It seemed to work with the linux-image-2.6.3-386 kernel package. But not with anything newer, or with the -686 nor -k7 kernels, which should be appropriate for this AMD Sempron 2500+ CPU, I get no sound output. The snd_via82xx module still loads and all the apps act happy, but no sound comes out.

My ubuntu hardware submission ID is 3cec243e16699c5b07444b23266ef797; I can't seem to make any use of that, but maybe you can.

Here are some details that, I gather, are relevant to diagnosing sound problems:

connolly@amdantec:~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: V8237 [VIA 8237], device 0: VIA 8237 [VIA 8237]
  Subdevices: 4/4
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
card 0: V8237 [VIA 8237], device 1: VIA 8237 [VIA 8237]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

connolly@amdantec:~ $ lsmod | grep snd
snd_seq_dummy 3716 0
snd_seq_oss 33664 0
snd_seq_midi 9184 0
snd_seq_midi_event 7040 2 snd_seq_oss,snd_seq_midi
snd_seq 51024 6 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_seq_midi_event
snd_via82xx 28672 0
gameport 14920 1 snd_via82xx
snd_ac97_codec 84028 1 snd_via82xx
snd_pcm_oss 53152 0
snd_mixer_oss 19392 1 snd_pcm_oss
snd_pcm 89032 3 snd_via82xx,snd_ac97_codec,snd_pcm_oss
snd_timer 24260 2 snd_seq,snd_pcm
snd_page_alloc 10696 2 snd_via82xx,snd_pcm
snd_mpu401_uart 7360 1 snd_via82xx
snd_rawmidi 25056 2 snd_seq_midi,snd_mpu401_uart
snd_seq_device 8524 5 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_seq,snd_rawmidi
snd 55172 11 snd_seq_oss,snd_seq,snd_via82xx,snd_ac97_codec,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_timer,snd_mpu401_uart,snd_rawmidi,snd_seq_device
soundcore 9696 1 snd

connolly@amdantec:~ $ lspci
0000:00:00.0 Host bridge: VIA Technologies, Inc. VT8377 [KT400/KT600 AGP] Host Bridge (rev 80)
0000:00:01.0 PCI bridge: VIA Technologies, Inc. VT8237 PCI Bridge
0000:00:09.0 Ethernet controller: Atheros Communications, Inc. AR5212 802.11abg NIC (rev 01)
0000:00:0a.0 Multimedia video controller: Brooktree Corporation Bt878 Video Capture (rev 11)
0000:00:0a.1 Multimedia controller: Brooktree Corporation Bt878 Audio Capture (rev 11)
0000:00:0f.0 IDE interface: VIA Technologies, Inc. VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 06)
0000:00:10.0 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 81)
0000:00:10.1 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 81)
0000:00:10.2 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 81)
0000:00:10.3 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 81)
0000:00:10.4 USB Controller: VIA Technologies, Inc. USB 2.0 (rev 86)
0000:00:11.0 ISA bridge: VIA Technologies, Inc. VT8237 ISA bridge [K8T800 South]
0000:00:11.5 Multimedia audio controller: VIA Technologies, Inc. VT8233/A/8235/8237 AC97 Audio Controller (rev 60)
0000:00:12.0 Ethernet controller: VIA Technologies, Inc. VT6102 [Rhine-II] (rev 78)
0000:01:00.0 VGA compatible controller: ATI Technologies Inc Radeon RV100 QY [Radeon 7000/VE]

See also: <a href="http://dm93.org/2005/0501pchw/index.html">notes on building this PC</a>, <a href="http://dm93.org/z2001/AmdAntec">more notes about this PC</a>.