AMD Radeon HD 5770 1GB kexts for yosemite

[Fl0r!an]

I don't know your exact card, but I'd expect that the AMD kexts don't contain the device id of your card. Did you try to add them to the Info.plist of the kexts or fake the device id of your card (e.g. with the ID of the well-supported 6870)?