Are you running the stock BIOS? I flashed johnlewis's ROM and can successfully boot
F22 media. I initially had to do F20->F21->F22. Flashed the ROM, ran Debian for a
while, and then
went back to a minimal F22 install. I don't recall having any issues booting Fedora
media after flashing the BIOS.
I followed these steps:
https://blogs.fsfe.org/the_unconventional/2014/09/19/c720-coreboot/
More reading:
https://johnlewis.ie/custom-chromebook-firmware/rom-download/
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jmz(a)sdf.org
SDF Public Access UNIX System -
http://sdf.org