Not recognising more than 6gb

I just purchased a new Mac Pro 2 x 2.8 quad xeon, it came with 2 x 1gb ddr2 FB-DIMM 800mhz, i've tried to add an extra 4 x 2gb ddr2 FB-DIMM 800mhz matched pairs in banks 2,3,4

The memory is recognised in only bank 3, it seems bank 2 and 4 are not working, or am i doing something wrong?

Thx in advance

I would suggest pulling the factory RAM, installing 2 sets (4 sticks) of the new in the appropriate banks. See what you get then add the next set. Mac Pros work the best when both boards are used so the first 2 matched pairs one should be on each board. Do a search there is a layout recommendation for adding RAM in the best order.

Yeah its my guess that you got the layout of the banks wrong, its an easy mistake to make.

The Mac Pro will "see" at least 8 GB of RAM - that is what I have in mine and it all shows up. Keep working at it, you will get it.