For my 4.0 gHz oC on the 9650 I got it stable with these settings...

400fsbx10

Ram linked with 3:2 ratio for 1066 mhz 5-5-5-15 (Ballistix 1066)

voltages Im using,
vcore 1.425
fsb 1.3
spp 1.45
mcp 1.525
ram 2.2v