SiS today officially released Chipset drivers AGP 1.11 on their website:

Seems to be the first driver to support AGP8x transfer rate for SIS chipsets. Works with all SiS chipsets from 630 and higher and might work with all previous SiS AGP chipsets . There is a newer AGP 1.12 floating around but seems to be more beta.

SiS648 , SiS645DX , SiS645 , SiS651 , SiS650 , SiS745 , SiS740 , SiS735 , SiS733 , SiS635 , SiS633 , SiS730 , SiS630.

SiS Driver Page

Download Official SiS AGP 1.11 Chipset Drivers

Mirror #1

Mirror #2