CPU: SIS55x SIS550 SIS551 SIS552
Here is the config-2.6.25.4-norhtec I use. Maybe you can use it too - as a hint for your own use.
The message below comes in dmesg when you did not apply the patch-2.6.30-rc5-sis.
Linux version 2.6.30-rc5-norhtec-sis (root@norh) (gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)) #1 Sat May 16 03:54:58 CEST 2009 KERNEL supported cpus: Intel GenuineIntel AMD AuthenticAMD Cyrix CyrixInstead NSC Geode by NSC Centaur CentaurHauls Transmeta GenuineTMx86 Transmeta TransmetaCPU UMC UMC UMC UMC CPU: vendor_id 'SiS SiS SiS ' unknown, using generic init. CPU: Your system may be unstable.
by Hans Schou