umm, do you really think you should be overclocking? you sound like you need to have a more thuro understanding before you atempt it
the p4 FSB is 4 x 133, DDR 400 runs at 2 x 200, so underclocking the FSB will only lower performance, especially with dual ddr, essentially with two sticks of ddr you will have a theroretical speed of 4 x 200 running on an FSB of 4 x 133
and buy which ever board suits your fancy, sis 655 is faster in your config, but is know to have RAM compatibility issues, intels chipset is rock stable, and will work with your pc 3200
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