Hi murrica:
I don't know what MSI designated those slots as on the motherboard. Let me just label them as slot #1, 2, 3, 4, 5 6.
I have been using slots #1, #2, #3, #4 for the past 2 years. #5 and #6 were not used. It seemed to me as if #1 is the base slot. So I use that as reference...