Intel ICH4 : unable to map IO port space

[Seb]

Hello
I'm running FreeBSD 5.2.1 Release on a laptop computer equipped with the
Intel ICH4 82801DB audio chipset. Sound doesn't work at all, and I have the
following error message in the kernel log :
pcm0: <Intel ICH4 (82801DB)> port 0xe100-0xe13f,0xe000-0xe0ff at device 31.5
on pci0
pcm0: unable to map IO port space
device_probe_and_attach: pcm0 attach returned 6
I've searched the Web and mail archives, and tried to change the values of
pci.allow_unsupported_io_range and hw.pci.enable_io_modes, without any
effect.
Some messages said that setting the BIOS to "Non PNP OS installed" can solve
this problem, but I don't have this option in my BIOS, and no upgrade is
available for it.
When I boot with ACPI disabled, I still have the same error message,
moreover the whole system crashes right after it with a general protection
fault.
The sound used to work under Linux.
Thank you for your help,
Sebastien