The default ChipSet name for this driver is "ati".
If "ativga" is specified instead, the driver will not use any ATI accelerator CRTC it detects, relying instead on any detected ATI VGA CRTC to provide the screen image.
A ChipSet name of "ibmvga" enables the driver's generic VGA support, but only for non-ATI adapters. If an ATI adapter is detected, the driver will operate as if "ativga" had been specified instead.
For compatibility with other XFree86 servers, both past and present, that support ATI adapters, the driver also recognizes "vgawonder", "mach8", "mach32" and "mach64" as chipset names. In this version of the driver, all such names are equivalent to "ati". In some future release, each name will have a different meaning to be documented at that time.