Bitfields for Cirrus Logic user options word:
Bit(s)	Description	)
 1,0	centering
	00 vertical centered, 01 from bottom, 10 from top, 11 reserved
 3,2	720-dot fix-up options
	00 OR every 8th and 9th pixel
	01 display MGA mode from left
	10 display MGA mode from right
	11 skip every 9th pixel
 4	???
 7-5	video mode (001 CGA, 010 MGA, 011 EGA, 100 VGA)
 8	external monitor enabled instead of LCD panel
 9	vertical expand mode enabled
 10	8-bit mode instead of 16-bit mode
 11	normal video rather than reverse video (for LCD)
 12	attribute automap rather than attribute emulation
 13	bold mode disabled (default)
 14	fast bandwidth
 15	???