If I recall correctly, at least some of the STM32F4 timers can be clocked at the same frequency as the system clock, so 168MHz maximum. The GPIOs can be config

If I recall correctly, at least some of the STM32F4 timers can be clocked at the same frequency as the system clock, so 168MHz maximum. The GPIOs can be configured with a maximum 100MHz clock, though your software likely cannot read the registers that quickly if it is going to do much else. EDIT: The reference manual actually contains a lot of the peripheral details, with the datasheet containing the chip specific details, like clock speed and which peripherals are present. http://www.st.com/stonline/stappl/resourceSelector/app?page=fullResourceSelector&doctype=reference_manual&LineID=1035 http://www.st.com/stonline/stappl/resourceSelector/app?page=...