Int 10 Fn 05  - Video - PCjr - Manipulate Crt/cpu Page Registers           [V]

   AH = 05h
   AL = subfunction
       80h read CRT and CPU page registers

       Return: BH = CRT page register
           BL = CPU page register
       81h set CPU page register
       BL = CPU page
       82h set CRT page register
       BH = CRT page
       83h set both CPU and CRT page registers
       BL = CPU page
       BH = CRT page

Notes: the CPU page determines which 16K block of the first 128K of physical
     memory will be mapped at B800h by the hardware
   the CRT page determines the start address of the memory used by the
     video controller