sys/dev/ipmi/ipmivars.h contains the following definition: #define MAX_TIMEOUT 3 * hz This determines how long ipmi(4) is willing to wait in its attach routine for the management device to identify itself. Unfortunately, it is too short. The IPMI specification recommends a timeout not less than five seconds, and in practice on this platform it takes between five and ten seconds. Fix: Increase the timeout to ten seconds. If this is felt to be too long, make it a tunable. How-To-Repeat: Boot FreeBSD on a Quanta QSSC-S99Q server. Sometimes ipmi will attach; most of the time it will time out.
Fixed by sbruno in r253812.