http://www.winischhofer.eu/linuxsispart1.shtml
DRI:
* DRI ("Direct Rendering Infrastructure") is the basis for OpenGL and hardware 3D acceleration. Without DRI, X.org/XFree86 will use software rendering for OpenGL and 3D which is really slow.
* The X driver this page is about has nothing to do with DRI. Instead, a separate driver is needed for this feature. This separate driver is developed by the DRI developers. I do not do any DRI related development, hence asking me questions about DRI is useless (and such questions won't be answered).
* DRI is only supported on the 300 series (300/305, 630, 730). A DRI driver for the SiS 300 series is provided by XFree86 4.1, 4.2(.1), XFree86 4.4 and X.org 6.7.0 and later. XFree86 4.3 does not contain a SiS DRI driver; However, installing the drivers from 4.2(.1) works well.
* Once again: There is no DRI/OpenGL/3D support for the SiS 6326, 5597/5598, 530/620, 315, 550, 650, 651, 740, 330, 661, 741, 760, 761 including all model variations with letters in the model number.
* About XGI: Although there is a binary XGI DRI driver for the Volari Vx chips available from XGI, this DRI driver is not supported in connection with the X driver available here or in X.org/XFree86. Hence there is no DRI/OpenGL/3D support for the XGI Volari V3XT, V5, V8 chips yet, unless you dare to use XGI's "own" X driver which comes with the said binari DRI driver. (The Volari Z7 has no 3D engine, so thinking about DRI is moot.)
* For a little more information on DRI on the 300 series, see here.