MYawar :
https://www.newegg.com/Product/Product.aspx?Item=N82E16813138424&cm_re=ddr4_2133-_-13-138-424-_-Product
This motherboard is very cheap and i dont know why. Is it fully compatible with a i5 7400? I know i will have to update the bios on the motherboard. Anyone know how i can do that?
It's cheap because it's using a more basic chipset, so only supports lower memory speeds, no overclocking and so on.
That said, according to Biostars website it support the 7400:
http://www.biostar.com.tw/app/en/mb/introduction.php?S_ID=825#cpusupport
Note in the cpu support list there is an asterisk next to all the 7xxx processors- I'm guessing that means you'll need a bios update to fully support the cpu (shouldn't be a problem just worth noting).
The board specifies solid caps and has a full PCIe x 16 slot for a graphics card so looks fine to me if you aren't interested in overclocking (also note it only has 2 memory slots for ram so not ideal for future expansion of memory).
Edit: Looking at that asterisk- it says lower down you need to update the bios *before* using a kaby lake (7000 series) cpu. If you are building from scratch it might be easier to stick with Skylake unless you desperately need a Kaby Lake cpu (the only difference is related to the video decoder, otherwise the cpu's are essentially the same) so look at a a 6xxx i5 instead if you go with that board.