PORTIBM PC Portable (uses same BIOS as XT) 0028-002A - 80486 "Deep Green" motherboard - ???

0028  ?W  index for data port
002A  RW  ??? data port

Note:	in order to access to the registers available through PORTIBM PC Portable (uses same BIOS as XT) 002A,
	  an unlocking sequence must be written via PORTIBM PC Portable (uses same BIOS as XT) 0028:	write
	  A0h, 05h, index to PORTIBM PC Portable (uses same BIOS as XT) 0028, then read/write PORTIBM PC Portable (uses same BIOS as XT) 002A, then
	  write A5h to PORTIBM PC Portable (uses same BIOS as XT) 0028