I would guess that somewhere in the 12.0 part there is a "magic bit" you can set that makes 12.4 not even visible to a config cycle -- i.e. a bios or os won't ever see that 12.4 as existing. This is really common in these types of parts. Do you know if this is the case?
Well, I described that somewhere.
The datasheet for cs5530 says, that the integrated graphic unit which seems located at 12.4 provides a ramdac and other stuff for vga output, like a rgb signal and digital Pixelbus, but the main graphic computing is done by the GXM Cyrix in this case.
This board was manufactured in many ways, like the epia itx serie. The core is always the same, but the peripherie differs.
In my case there are pads for a LVDS connector, which seems to wired to the cs5530, but the connector is not "on board". You know what I mean :D
In Factory Bios you can enable/disable this feature. Called TFT/Display or so. I will make a lspci after enable. If I remember right, enabling this feature disables the onboard cyberpro graphic chip (9.0)
It could be, that both devices can not run at the same time. More we should find this bit ;)
ron