what's the best cpu that can fit a78m-e35 mobo



i have now a amd a4-5300 apu radeon
and i recently bought a amd athlon x4 845k and it seems it doesn't work , got black screen and keyboard light is off and the rest in the pc is working and blowing and no beep sound. so what could be a problem ? how do i update my BIOS or know i have a old version of it?
 
It's worth mentioning that you might want to consider upgrading CPU and mobo together for a more "future proof" build. You're currently considering upgrading an outdated motherboard with increasingly outdated CPU's...