Did you take a PC that had another CPU in it and simply switch it for a Bulldozer FX-8120 without re-installing Windows?
If you did... reinstall Windows.
Second thing... update your BIOS to make sure it is running the latest version for full Bulldozer support.
i got the motherboard and 8120fx new 3 days ago. i also got 16 gig of ram that dont show either ony 8 ? n i did flash the bios to the newest version? as well as a fresh install of vindows 7 64 ultimate ?
re-seat your ram, even try putting it in different slots. As for the 8 core only reporting 4 thing, where are you looking for this information? windows task manager?