For newer systems, running without ACPI is often problematic, fortunately there does appear to be BIOS updates available for that motherboard.
You may wish to try upgrading and seeing if that helps things any.
http://support.asus.com/download/dow...A785TD-V%20EVO
You should work with the developers to get this fixed, use
acpidump(8) to send a dump to
marco@ (Marco Peereboom) and
jordan@ (Jordan Hargrave), they are the primary ACPI developers.
Only send the resulting binaries using
-o, in the form of a tarball, apparently acpidump's AML parser was broken and removed from -CURRENT.
You don't need ACPI enabled in the kernel, the following dumps the files into the current directory.
$ sudo acpidump -o asus-m4a785td-v-evo
The only other thing I can think of is looking around the BIOS settings, while reading through the motherboard documentation.