The following options are of particular interest for the SiS driver. Each of them must be specified in the Device section of the XF86Config file for this card.
This option lets you to modify the memory clocking of your card. (only for 5597 and 6326) Modifying the memory timings can destroy the device, but usually the only ill effects of overclocking is to have some noise an drawing errors, but BE CAREFUL. Usually a little increment can improve the drawing speed, and allows also higher dotclocks. The server reports default memclock on starting messages, so take it as a base. Units are in KHZ.
This option lets you to modify the maximum allowed dotclock).
The default is for using the hardware cursor.
5597/8 and 6326 have the option to extend the engine command queue on VRAM. With extended queue length, the driver only checks queue status on some color-expansion commands. This gives some performance improvement, but is possible to lose some commands, corrupting screen output. As the size of extended command queue is 16-32K, the probability is very low, but exists. The performance gain observed is around 8-10%. Currently, using this option will occasionally freeze the acceleration engine, causing weird image display.
Enables 1 cycle memory access. Try it. Increased memory bandwidth reduces the possibility of glitches and noise on high resolution modes.
Disables various hardware accelerations.
The SiS chips can only directly address 4096K bytes of video RAM. Some video cards using these chips are shipped with additional video RAM. The videoRAM must be explicitly limited to 4096 for those cards. Attempting to use the additional RAM leads to a variety of scrambled screen artifacts.