In our quest to unlock the performance of our AM3 X3 710 processor, we found that the new boards still did not fully disable this function in the AMD 890GX series boards.
In fact, instead of enabling it through the cumbersome ACC, some boards offer hardware switches to unlock the cores. Of course, you would have to pair it up with a processor like Phenom II 550BE or Phenom II X3 710 to enable the hidden cores (these two processors are proven to unlock easily).