Question Athlon x4 845 wont post

[kobacc]

My friend bought a new Athlon x4 845 CPU,and when he tries to boot it he gets a black screen,when he puts back his old a4-4020 it works fine
His specs are:
Gigabyte GA F2A55M-S1 (rev 3.0) mobo
Athlon x4 845
2x4GB RAM
R7 250 GPU
He updated the bios to the latest version,reset the CMOS,tried with 1 RAM stick,tried connecting the monitor to the mobo instead of the GPU outputs and it still doesnt work,but with the old cpu it works fine

 

[Obakasama]

If the motherboard model is accurate then it looks like the x4 845 isn't supported: https://www.gigabyte.com/Motherboard/GA-F2A55M-S1-rev-30#support-cpu

From memory the x4 845 was pretty much the last FM2+ CPU released and a different architecture (Carrizo, I believe). The lack of BIOS support and the previous CPU working would seem to confirm the incompatibility.