Right,

If you drop a 512 chip into all 3 orange slots does it boot up ?

Then, if you drop a 512 chip into each of the 3 purple slot's does it boot up ?

I have a suspicion, that you can only use one set of slots, unless, there's an option in the bios to enable all 6 to work well. What's the ram limit on the board ? It may also need a BIOS update. And be particular to what manufacturer's ram you put in each of the channels