I'm surprised at no serial out. It makes me think the initial assembly startup is quite wrong. The cbfs doesn't get involved until long after ram is up and working.
double check the jmp at fffffff0.
Since the image I built worked on qemu, I think the jumps should be there and correct. Uwe, have you tried running the image you built on qemu? I know it fails soon, but at least there's serial output.
Thanks, Myles