What does CPU-Z show?
Does Windows show 2 cores and 4 logical cores?
because the FX processors have modules with 2 cores each that share some common core components. So Windows sees the FX Module as a "Core" with 2 logical Cores.
EDIT: I have a FX8350 and in Windows it shows it has having 4 Physical Cores but 8 logical Cores but under CPU-Z it shows having 8 Cores and 8 Threads. In Device Manager under Processor it show 8 cores enabled.