I have Asus b450 rog strix E
Asus phonix dual gtx 1650s
AMD R5-3600
which clocks to 4200MHz while gaming. even that it's in stock mode
?why isn't it at 3600MHz
The maximum turbo frequency for that chip is 4200MHz.
As long as it's cool enough it will boost performance above the base 3600MHz when needed.