ppu setup:
  writes to 2006
  pointer setup
  tile row = 0
  meta row = 0
  meta tile = 0 (beginning of row)

meta row loop:  (0-5 = 6 rows of meta tiles on screen)

meta tile loop:  (0-7 = 8 meta tiles per row)
  load tile
  write tile
  add/write 3x more
  iny

  add 1 to meta tile
  if meta tile is not 8, go up to meta tile loop

  meta tile = 0

  add 1 to tile row (0-3 = 4 rows of normal tiles per meta tile)
  if tile row = 4, all done with that meta tile row, so go down to next meta row
  if tile row is not 4, subtract 8 from Y (rewind to start of row), go up to meta tile loop to repeat the same row again

next meta row:
  tile row = 0
  add 1 to meta row
  if meta row is not 6, go up to meta row loop

all done