If you remember, users are excited with Phenom II X3 710 or Phenom II 550BE as such processors have hidden cores that can be enabled by ACC feature which is supported on the SB710 or SB750 south bridges. Unfortunately, this won’t work with AMD 890GX as it is now paired with SB850 south bridge since the ACC feature is no longer available.
ASRock seems to have found a way to enable the hidden cores without ACC, they call it UCC (Unlock CPU Core). Not only 890GX board, ASRock also implemented it on entry level board NVIDIA N68 boards.
Below is a video which demonstrates how it is done using the ASRock