Can you try
- Enter BIOS
- Advanced Menu
- Select "Chipset"
- Set "MemClock Mode" to "Auto"
And check the FSB-DRAM ratio again?

(if it doesnt change anything go back and set it to 400 again)
From your 3dmark stuff, they seem to fall in line with expected values ... do you have any other games u can use to test? (say UT2004? doom3? splintercell? farcry etc?)
Here is a bios update for your board
There may be updated drivers
here
Lionhead studios has also released the
1.1 Update