We need more information than that. PC brand model or if home built motherboard specs etc. Plus do not use the thread header to ask your question. Type the question where you typed help. Header would be something like "AMD x840 cores problem". So with info right now I would check to see if the CMT is enabled in the BIOS. CMT is the AMD term for hyperthreading.
MSI A78M-E35 V2 not utlising four cores on my AMD x4 480? it will only run on 1/2 cores and windows wont let me select more than two PLEASE HELP OH GOD HELPPPPPPPPPPPPPP
Where does it not show 4 cores on ther task manager or the BIOS? check to see if the CMT is enabled in the BIOS. I want to see what CPU-Z states download and than run it look at the bottom right for the cores info. IF it states 4 than something is wrong with the mobo.
go to your BIOS settings, in the OC menu, make sure "CPU core control" is set to AUTO.
If the task manager / performance / cpu shows 2 cores and 4 threads, that is normal since it sees 2 steamroller modules which is interpreted as 2c/4t by the OS.