I haven't made much progress since I found a way to continue on this.
   I've been stuck horizontal, my body writhing. But it's still so much
   fun to know I found a way forward :) It's just nice to think about.
   When my setup stopped working it was so frustrating, and now I can
   continue again!
   While I was working recently I accidentally put my last flash chip in
   backward and powered the system up. When you do this the chip begins
   bheating up rapidly and then burns out. I walked away, not realising,
   and then turned around and pulled it out before it burned out. It was a
   big relief. I had identifying tape on the chip that partially melted.
   It still works though!
   I wrote some assembler code to boot up the serial port before the ram
   was initialised, to debug early boot, and after using the setup to
   verify it worked I shared it with the devs, but just casually not with
   a pull request yet. I've realised while daydreaming and such that the
   code has a bug that doesn't express: it checks for the serial data port
   being ready using the 8-bit port command rather than the 16-bit one. So
   it's actually reading from the wrong io port (8-bit truncated) and
   waiting for timeout rather than detecting readiness. I don't know why I
   didn't notice a compiler error, passing a 16-bit port number for an
   8-bit operand.
   Today I'm expecting a cheap breadboard in the mail to replace the ones
   that might be broken, and tomorrow a set of round pin headers to use as
   buffers to prevent breaking the new breadboard with square pins.