So I am building a pc for my friend and this mob has 2 eatx12v one with 4 pins and the other one with 8.
Do I need to connect something on them?
If you are talking about any of the Asus Republic of Gamer boards then that is an extra power plug for doing extreme overclocks with Liquid Nitrogen/Helium or Phase Change cooling. The only one that is required to be plugged in is the 8-pin, the 4-pin might help for high overclocks but it's really only needed for Liquid nitrogen/helium or phase change evaporators.
Well I installed everything by now, but I am not being able to start the PC i get the 1 code 99.