Apu 3 ghz ?

hello

 

i have a question

i start a game World of Warships and my Apu have 3 GHz

when i Close the game than i have 4,2 GHz

i dont why

i have this Only with World of Warships, all another games my Apu have 4,2 GHz

sry for my english

 

System

A10 7890k + MSI r7 250 (dual grafik)

Asus A88xm-Plus board

Corsair Vengeance pro 2x 4gb ram 2133 mhz

 

its not overclock