Full turbo speed requires disabling all but one CPU core, and running an application or benchmarking tool that will maximize the CPU speed. You cannot get full speed out of the CPU in multi-core (i.e., normal everyday) operation.  
My Alienware m17 R4 2021 laptop does not pass 4GHz? It should go to 5GHz. What can I do?  
m17 R4, does not pass 4GHz