cmBoardUpTime is a read-only TimeTicks counter giving the elapsed time since a specific card last powered on, independent of the system uptime. An administrator compares it against the chassis-wide uptime to identify a board that rebooted on its own, which points to a hardware fault or watchdog reset rather than a planned system restart. For example, if the SCM shows weeks of uptime but a single DSL line card's cmBoardUpTime reads only a few minutes, the operator knows that card reset unexpectedly and should investigate it.