For the Savage IX driver, as per this description from S3 Super Savage IX/C page on the ThinkWiki:
Direct Rendering (a.k.a accelerated OpenGL)
Works without any external drivers with Xorg7. After hibernate (suspend to disk) DRI will not work correctly. glxgears runs fine but playing games will hardlock. Workaround to prevent this is rebooting X. After suspend to RAM it works somehow but rebooting X is recommended.
I think although it's already supported by the kernel driver, it's too old for Unity which requires good 3D support.
S3 also provides Linux driver for this chip on their website, but it's really outdated and it reaches the end of support.
I would suggest you to give Lubuntu or Xubuntu a try. They use the light-weighted desktop system, LXDE and XFCE respectively, which are designed for low-spec and legacy hardware. You could find some more details from the following wiki page.
https://wiki.ubuntu.com/Lubuntu
https://wiki.ubuntu.com/Xubuntu