It's probably easier and less risky to just fit a PCI IDE controller card [they're so INEXPENSIVE].
I fitted one, it provides practically unlimited HDD drive capacity, and it frees up the internal IDE controllers. So now each of my optical drives has their own controller and therefore all three drives [there's now capacity for four to do this] can run concurrently.
No longer any of the business of having two drives on the same controller and attempting to read from one and write to the other so that they're forced to take turns; one reading, stop, the other writing, stop, first one reading again, stop, second writing again, stop,.... Ouch!
So you see, you get very useful extra capability for very little cost with no risk of turning your motherboard into an ornament.