Bitfields for RM386 global flags 2:
Bit(s)	Description	)
 0	HMA in use
 1	XMS present
 2	using XMS driver memory
 3	HIGH (NEAT only)
 4-7	reserved
 8	NOBKTRAP
 9	NORESET
 10	ALTMAP
 11	NOFRAME
 12-15	reserved