S3 Texture Compression can be forced in the intel open source driver. The code that does the option check is in intel.context.c. Search for „force_s3tc_enable“. As you can see the option is only checked when the context of „Mesa_DXTn“ is not available. „Mesa_DXTn“ is an external library that is not included in the mesa source code as the algorithms used in the DXT formats seems to be covered by patents in the USA (What patent no.?). The initial support of the external DXTn library was added in this commit. The source code of the DXTn library is available here. So you can checkout the source and compile the library for yourself. You need to put the compiled library (called „libtxc_dxtn.so“) in your library path. Beware that the preprocessor option „USE_EXTERNAL_DXTN_LIB=1“ in the mesa library needs to be set to make this work (this is true for Fedora 13, 14 and 15). With the software support in place you don’t need to force the S3TC support via the driconf option. This is the patent granted in the USA that seems to cover the S3TC. The DRI homepage also has something to say about S3TC.