these are kinda stragnge questions. the ram is compatable, your mobo supports up to ddr2 1066 Mhz ram. that means it will run will all ddr2 ram 1066Mhz and down.
and no it doesnt matter what nortbridge chipset you have if you are running a single graphics card setup.
The number they like to list in MB specs is just for marketing. It's really a statement of how fast the front side bus will run. DDR2 800Mhz RAM will be fine, especially if it runs at 1.8V.
Any single PCI-E video card will run on any chipset, as long as the board has a PCI-E slot. If you wanted to add a second 4850 then you would want a P45, x38, or x48 chipset.
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