Each time I turn off the power of the PC totally the bios settings change to its default, maybe. specially I see that the Bios time change to wrong time and iGPU which I have enabled it is changed to disable. I check the CLRTC jumper and it is in its default mode. Does the problem comes from its CMOS battery or I have to set something to fix it?
I have an Asus z68-v with the exact same problem, i would check the voltage of the cmos battery to see if it is ok, or just change it if you have a spare one. In my case it wasn't a problem with the cmos, so i suspect it is a problem with the mobo itself, currently i use an UPS so that i don't loose my setting in case of a power loss
The first thing to do would be to check the CMOS battery. It should be around 3.3V if memory serves. You could also replace it if you don't have a multimeter, as it is a relatively inexpensive component.
thanks for your answers. I am an electronic engineer and have multimeter in home but as I know in many times the weak batteries will show their nominal voltage on the voltmeter because input impedance of the voltmeter is very high and doesn't get any current from battery to pull down its output voltage, but when use it in a circuit it can not provide enough current and good potential differentiation in the circuit. So do you mean I have to measure its potential when it is assembled on the board?