Is here someone who wants to work on this perhaps together with me? (of course donations welcome ;) I will buy some / work on that only if someone else buys it too.
I've started porting coreboot to the ASROCK FM2A88M-HD+ (A88X chipset) and have nearly finished the code for the SIO chip used on that board (NCT6776). Will upload that soon, but still have to do some cleanup and verify some stuff with the datasheet.
If you'd like to help me with that board, I'd donate you a FM2A88M-HD+. But until august I sadly only have time for coreboot-related stuff on the weekends.
The only downside of that board is that the PCIe x1 slot is located next to the PCIe x16 slot; so if you want to use a fast graphics card the only PCIe x1 slot gets blocked mechanically.