Don't use the 1 multiplier on older chipsets.
Don't use the 1 multiplier on older chipsets.

  It is not in the specs, so don't use it on chipsets older then the 502.
  Some review should be done in SMI501_FindPLLClock() as when hardcoding it
to use the clock selection code for older chips, it appears to choose a
better refresh rate (no flicking at 1024x600).

lumag/xf86-video-siliconmotion,lumag/xf86-video-siliconmotion