/This was written for a much older computer than my present working machine. I leave it here because it may help someone else./
Because of the antiquity of this hardware, it cannot take advantage of the acpi power-management system in FreeBSD. That means we must disable acpi and enable apm. (Newer hardware means that this is no longer a problem for glynthebearded, but I leave this information here in case it helps someone else!)
Re-build the kernel to include apm support. The line
device apm
Make sure that /boot/device.hints includes these lines
hint.acpi.0.disabled="1" # this turns off acpi
hint.apm.0.disabled="0" # this turns ON apm
hint.apm.0.flags="0x20"
Insert these lines in /etc/rc.conf
apm_enable="YES"
apmd_enable="YES"
**Step 4
Re-boot! "shutdown -p now" should power down nicely.......