Using kernel 2.4.0-0.99.5 (2.4.0-ac9-based), on a Dell Latitude CPiA
laptop.   This laptop is running Guinness, + the above kernel + modutils
2.3.21.  I can modprobe nm256_audio just fine, but when playing back audio
(mpg123 or xmms), only horrible sound comes out, and the following gets
streamed to dmesg:

NeoMagic 256AV/256ZX audio driver, version 1.1
NM256: Found card signature in video RAM: 0x27ec00
NM256: Mapping port 1 from 0x266c00 - 0x27ec00
Initialized NeoMagic 256AV audio in PCI native mode
Initialized AC97 mixer
Done installing NM256 audio driver.
NM256: Sound playback pointer invalid!
NM256: Sound playback pointer invalid!
(repeats endlessly)


[mdomsch@localhost i386]$ lsmod
Module                  Size  Used by
nm256_audio            68592   1
sound                  61936   1 [nm256_audio]
ac97                    3776   0 [nm256_audio]
soundcore               4368   5 (autoclean) [sound]
binfmt_misc             3568   0
ds                      7248   2
i82365                 12800   2
pcmcia_core            42880   0 [ds i82365]
autofs                 11168   2 (autoclean)
3c59x                  24016   1 (autoclean)
agpgart                23424   0 (unused)
usb-uhci               22192   0 (unused)
usbcore                49008   1 [usb-uhci]

lspci -vvx shows:
01:00.1 Multimedia audio controller: Neomagic Corporation [MagicMedia 256AV
Audio] (rev 20)
	Subsystem: Dell Computer Corporation: Unknown device 0088
	Control: I/O- Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B-
	Status: Cap+ 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort-
<MAbort- >SERR- <PERR-
	Interrupt: pin B routed to IRQ 5
	Region 0: Memory at f8c00000 (32-bit, prefetchable) [size=4M]
	Region 1: Memory at fda00000 (32-bit, non-prefetchable) [size=1M]
	Capabilities: <available only to root>
00: c8 10 05 80 02 00 90 02 20 00 01 04 00 00 80 00
10: 08 00 c0 f8 00 00 a0 fd 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 28 10 88 00
30: 00 00 00 00 dc 00 00 00 00 00 00 00 05 02 00 00

Note, there's no IRQ assigned in /proc/interrupts:
           CPU0       
  0:     114988          XT-PIC  timer
  1:       2704          XT-PIC  keyboard
  2:          0          XT-PIC  cascade
  4:          7          XT-PIC  serial
  8:          1          XT-PIC  rtc
 10:      18107          XT-PIC  eth0
 11:          0          XT-PIC  usb-uhci
 12:      26351          XT-PIC  PS/2 Mouse
 14:      14918          XT-PIC  ide0
 15:          0          XT-PIC  ide1
NMI:          0 
ERR:          2

/proc/iomem contains:
f4000000-f7ffffff : Intel Corporation 440BX/ZX - 82443BX/ZX Host bridge
f8000000-f9ffffff : PCI Bus #01
  f8c00000-f8ffffff : Neomagic Corporation [MagicMedia 256AV Audio]
  f9000000-f9ffffff : Neomagic Corporation [MagicMedia 256AV]
fbfffc00-fbfffc7f : 3Com Corporation 3c905C-TX [Fast Etherlink]
fd000000-feffffff : PCI Bus #01
  fda00000-fdafffff : Neomagic Corporation [MagicMedia 256AV Audio]
  fdb00000-fdbfffff : Neomagic Corporation [MagicMedia 256AV]
  fdc00000-fdffffff : Neomagic Corporation [MagicMedia 256AV]

The nm256.o driver works just fine with the 2.2.16-22 kernel on this
system.