Question Asrock Z68 Exterme3 Gen3 Bios does not save some changes

[dadashali]

My mobo suddenly does not save some settings like HDD priority and also does not detect more than 2 RAM slots at same time while it has four slots. Also On board VGA does not be detected.
I did CMOS reset and Bios flash but nothing changed.

 

[Dark Lord of Tech]

CMOS battery ?

 

[dadashali]

CMOS battery should cause a problem when the PC got unplugged while I can not save settings even after exiting the UEFI!
But I removed the CMOS battery also and unplugged the PSU for some mins but the result was same. With CMOS battery problem you can't save the date while in my case i can save the date!

 

[dadashali]

However, I have another problem with RAMs. My RAM bus is 1600Mhz and while my mobo could detect to 2133Mhz of RAM (before the present problem) at the moment it can not detect more than 1333Mhz bus!

 

[dadashali]

Any advice?