I have looked at the DisplayPort Aux traffic and the driver first reads the checksum of the base EDID. If it has seen the checksum before it does not read the full EDID. The checksum is one byte long, 256 possible combinations. The content of the base EDID is 127 bytes long. There are billions of possible valid base EDID modes.It is very easy to have two different modes that have the same checksum but the graphics card will not detect any change and will not change resolution. Attached are two EDIDs that describe very different modes but have the same checksum. Which ever the graphics card sees first is the only mode that the outputs will do.
Is there a fix for this?