I did a quick google search for "linux support sis chipset" and this came up: airis-laptop-debian-howto-en.html
looks like you need to get the sis DRI drivers here
. then install the compiled drivers to:
I would do an 'lsmod' to make sure they are actually loaded when all is said and done.
For more detailed instructions, it looks like the site you get the DRI drivers from would be a good resource.
Hope this was of some help.