Int 15 Fn C203  - System - Pointing Device BIOS Interface (ps) - Set Reso  [M]

   AX = C203h
   BH = resolution
       00h one count per mm
       01h two counts per mm
       02h four counts per mm
       03h eight counts per mm

Return: CF set on error
       AH = status (see AX=C200h)