Most micro controllers use Harvard Architecture is true.
Explanation:
Today's digital world all or most of microprocessor  or micro controllers are used Harvard architecture for better performance
In Harvard Architecture it is physical separate storage data and signal pathways and their instructions and data. Harvard Architecture is plays major role for small embedded computer and their signal processing (DSP).
For desktop or laptop von Neumann Architecture is been used.
Declaration:- for server side Harvard Architecture
For desktop von Neumann Architecture is been used.
For better performance some desktop or laptop use both Harvard Architecture and von Neumann Architecture.
