Making NetBSD 4.0 and OpenBSD 4.3 install in VirtualBox

Installing NetBSD 4.0 in VirtualBox fails with:
Failed to write to file. /usr/bin/dig (or whatever) (Bad address).

To make it work disable ACPI, enable VT-x and set the IDE controller type to PIIX4.

VT-x makes all the difference for NetBSD also. Without VT-x, unpacking install sets is very slow (200kb/s). With VT-x, I get 6.42 MB/s.

Plus, it won't fail writing to files.

The same thing happens with OpenBSD, and can be fixed by using VT-x.