SIS hasn't produced any actual graphics cards to my knowledge, they do make integrated graphics chipsets. What you have is an SIS graphics chip built into your motherboard.
You didn't specify why you needed to know this, but if you are wondering if it is capable of playing games, it most likely will not. SIS integrated graphics are quite weak when it comes to 3D rendering, they're even worse than most of intel's IGPs. If you are looking for gaming capabilities, you are going to have to look at a getting an actual graphics card. You would have to post system specs, including CPU, RAM, Motherboard, OS, Power Supply, Screen Resolutions, which games you wish to play, and a budget before we could make any recommendations on which card to get if you are interested in upgrading.
If your computer is a laptop, you are pretty much out of luck. Few laptops are upgradeable when it comes to graphics, only the very expensive gaming laptops can be upgraded, and none of those use SIS graphics.