This register contains the width and height of the blitter operation
(in line mode width must = 2, height = line length). Writing
to this register will start the Blitter, and should be done last,
after all pointers and control registers have been initialized.
H9 H8 H7 H6 H5 H4 H3 H2 H1 H0 W5 W4 W3 W2 W1 W0
H=Height=Vertical lines (10 bits=1024 lines max)
W=Width=Horiz pixels (6 bits=64 words=1024 pixels max)
SEE ALSO: BLTSIZV and BLTSIZH