[Coco] ML Question: Hi Res Text Screen

[William Mikrut]

It's been a long, lone time since I have been down this path.

Years ago I was working with Robert Gault and others and was able to
initialize and load graphic screens and the high res text screens from
assembly.

I know I can JSR to $F679 to set the default 80 column mode.

I know to manipulate registers FFB8-FF9E  for foreground colors and
FFB0-FFB6 for foreground (text) colors.

What I cannot remember, for the life of me, is which register controls the
top/bottom borders of the page?