Wow, that series looks fascinating!

Only watched the first video yet, after initializing itself the CPU actually runs this code (because D8-D15 is wired to zero):

  addr    opcode
  FFFFF0  90           NOP
  FFFFF1  00 90 00 90  ADD [BX+SI+9000],DL
  FFFFF5  00 90 00 90  ADD [BX+SI+9000],DL
  FFFFF9  00 90 00 90  ADD [BX+SI+9000],DL
  FFFFFD  00 90 00 --  !! general protection fault

You can see it read and write the same address three times, then fetch the interrupt 0Dh vector and push flags+CS+IP to the stack :)