Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Atmel/AT91SAM9M11/PMC/PMC_MCKR#0x0
Master Clock Register
Master/Processor Clock Source Selection
Master/Processor Clock Prescaler
Master Clock Division
PLLA divisor by 2
https://github.com/cmsis-svd/cmsis-svd-data