Comment # 27 on bug 86720 from Benjamin Bellec

(In reply to noga.dany from comment #26)
> I tried run it with nosb parameters like mentioned above "R600_DEBUG=nosb
> force_s3tc_enable=true /usr/bin/steam %U" and game works, but textures looks
> very bad.

Remove the "force_s3tc_enable=true" in your command.

And be sure to have the s3tc lib installed (libtxc_dxtn). You can check that
with this command:
$ glxinfo |grep s3tc