No reason I can think of to why you'de want to change your southbridge voltage anyway, you don't overclock the southbridge, you overclock the northbridge.
Edit* Never ran into an issue like that because I only use 1 HDD. Hopfully someone else can give you a better answer, sorry ^^

Edit* Never ran into an issue like that because I only use 1 HDD. Hopfully someone else can give you a better answer, sorry ^^