Enabling watchdog

[rihad]

Hi, I'm thinking of enabling the watchdog on our Dell PowerEdge 2950 / 
FreeBSD 8.0 amd64, so that it reboots the machine in case of lockups.
Right now it doesn't work:

# watchdog
watchdog: patting the dog: Operation not supported
#

Looking through the kernel configuration I found two relevant settings:
In /sys/conf/NOTES:
#
# Add software watchdog routines.
#
options SW_WATCHDOG


and in /sys/amd64/conf/NOTES:
#
# Watchdog routines.
#
options MP_WATCHDOG


Which of them should I rebuild the kernel with? BTW, the existing kernel 
is built with the default "options SCHED_ULE" to make good use of 
multiple CPUs, does watchdog work with it?

Thanks.