In a Quantum Hot Standby system, the Primary CPU and Standby CPU controllers have their own system timers, which are not implicitly synchronized.

At Switchover, the Standby CPU sets its system timer with values sent by the Primary CPU. This mechanism allows the new Primary CPU to run the Hot Standby application in the same context as the old Primary CPU.

If the timers are not synchronized, then at Switchover, the system timer would change by the difference between the two clocks.

Non-synchronous clocks can cause problems in a time-critical application.