I'm trying to use a live USB of Ubuntu Gnome 17.04 on my 2013 Mac Pro (trash can model). But I'm getting stuck in a loop during the text output during the booting process.
I have rEFInd set up (since I'm already running 16.04), and I select the USB drive to boot into Grub. I select boot from USB. I see the logo animate for a bit, which I'm guessing is gnome or gdm related. Then I get the following output on the screen in TTY (with times ommitted):
bmca: Unsupported SPROM revision: 11 bmca: bus0: No SPROM available sd 1:0:0:0: [sdb] No Caching mode page found sd 1:0:0:0: [sdb] Assuming drive cache: write through sd 2:0:0:0: [sdc] No Caching mode page found sd 2:0:0:0: [sdc] Assuming drive cache: write through
I can see the output disappear and reappear frequently, like it's getting stuck in a loop. I've searched these error messages, and they suggest disabling WiFi since it could be a driver issue. But I'm using rEFInd, which I don't think has that option.