On many modern laptops, ACPI is the only way to access some devices. Without it they can not allocate IRQs. On my laptop sound also does not work without ACPI. So, either enable ACPI or forget about internal soundcard. In my case I got Echo Indigo IO, as my intel_hda worked acpi-only and even then half-duplex. Not talking about sound quality :) Regards, Dmitry.
