you probably know this already, I just stumbled
We prefer 32 bit addresses over 64 ones if they are
not equal, which helped for some broken BIOSes
from pre-Vista times.
Now it's the other way around:
If the FADT Revision field is > 2,
Windows Vista will use the extended
64-bit addresses in the FADT
X_FIRMWARE_CTRL and X_DSDT
Extended addresses of ACPI fixed hardware
Just for info...