Try to enable Mode X-like memory organization for
256 color modes using up to 256K of memory like 320x200x256
and 640x400x256.
Modes like 320x240x256 etc. are Mode X-like by default.
vga_modeinfo (3)
lists which modes have Mode X memory layout.
A mode X like memory layout means that memory is organized in four pages
( set_page (3))
and that the top most pixel 0,1,2,3 are the first pixel in pages 0,1,2,3. Pixels
4,5,6,7 are than the second pixels in pages 0,1,2,3.
The other, packed pixel, mode will have pixel 0,1,2,3 as pixel 0,1,2,3 in page 0 and
so on. It will only use the next pages if the size of the first 64K page is exceeded. Most
SVGA 256 color modes work this way.
This is not guaranteed to work. Probably a new mode should be defined
for planar 320x200x256.