hi guys, wanna throw a noob question..

i have following this thread while looking for a motherboard to pair with i5 3570K CPU.. finally i choose Asus P8Z77-M since this is chosen by a few of the member in the first page.. after i finished setup everything including windows, i installed coretemp apps.. from there i can see, the CPU always go MAX at 3.8GHz.. is this auto overclock is done by Asus motherboard?? is it safe to let it go with the default heatsink??