AMD's construction core CPUs (Bulldozer, Piledriver, Steamroller, Excavator) share resources, so they're arguably somewhere in between a 2c/4t CPU and a true quad core. When you load up all 4 cores, there's a penalty to performance so it's not quite as fast as if the cores didn't have to share. The reason it shows up as 2c/4t in Windows task manager is that the cores are in "modules", or pairs of two, and Windows needs to be aware to load up only one core per module before loading the second - e.g. load up "cores" in the order of 1, 3, 2, 4, because 1 and 2, and 3 and 4 share resources, in the same way that on an Intel CPU with hyperthreading, you want to fill all of the cores with only one thread before adding a second thread to any core.
In Cinebench and Task manager it is showing as 2 cores 4 threads, I thought this was a quad core CPU?
hopefully i can explain this properly. but sometimes task manager reads information incorrectly. the athlon 880K is a FULL on quad core processor. it has 2 modules and within 1 module there are 2 cores. the only problem being that there is only 1 FPU per module. an FPU is a resource for each core. but since there's only 1 FPU per module there can only be 2 cores running at once. effectively making it a dual core processor under load.