Well, it looks as if the recent tendency to improve the performance of the chipsets has also touched SiS Company. Although, unlike VIA, they behaved a bit more modest and avoided excessive pomposity: no special press-releases, no "pseudo-new" chipsets with additional indexes. In reality everything is much simpler: SiS started shipping the new SiS645 chipset revision with A2 index. We learned about it when Soltek announced the launching of their updated SL-85DRS mainboard on SiS645.
News source: Designtechnica - SiS 645 gets beefed up!
News source: x-bit labs - SiS Speeds Up Its SiS645
