Problems with Processor Clock
There are two kinds of problem with using the processor clock register as a high precision clock
- Stability of the clock itself – stability is not a major goal in system design
- Long term drift – e.g. temperature dependence
- Short term oscillation – clock jitter
- System management changes to gross clock rate
- Power management – lower speed reduces power
- Response to over-temperature in some systems
- In portable systems, low power idle state may stop clock