The Q650 and Q700 boards are a similar form factor and the Q700 has the extra slot that you mentioned. I discovered that when building my rehoused Q700 in IIvx case. I bought an overclock kit for the 040 and it included a board that fits into the slot on the Q700 board. The Q650 does not have this slot. The upgrade kit also says it works with the Q800, so your board with the slot may also be a Q800 board.