Intel motherboard dx58so RAM slots

The Intel DX58SO motherboard has support for tri channel memory. You will not use the black slot, unless you are using single channel memory. You need to put your three ram dims in the blue slots. I have the exact same motherboard and I can understand your confusion. Be sure to read the manual.

I just finished configuring the Intel DX58S0 MB
It was not fun.
While I won't say for sure just yet....it seems that it's not too stable with that black slot occupied.
Fortunately, I did read in some documentation that memory use will not be optimized when it is used, but I had to try, anyway.
Well, it's like this - I can't even get it to boot up properly when I use the 4th slot.
WHAT THE HELL KIND OF MB IS THIS THAT YOU CAN'T USE THE SLOTS THEY GIVE YOU!!!
Not to mention that is seems to have issues with an IDE adapter I installed. I know we're all modern here and all that, but are we really ready to totally S***can IDE adapters on a MB?
While I'm sure much of my difficulty was of my own making, I still gotta say I am not a big fan of this mother!