i think you are out of luck ... the proprietary sis drivers are for old version XFree 3.3.6 ... F8 uses much newer X.Org ... the 630/730 are old chipsets. .. Suggest you buy a new nvidia card which has 3D hardware support from livna, or revert to an older version of X.
* AMD Phenom 9750, 8GB DDR-1066, Gigabyte MA770UD3, ATI X550, F12 64bit
* Dual Athlon MP2800+, Gigabyte GA-7DPXDWP, 1GB, Centos 5.4