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

   AX = C203h
   BH = resolution (see #0447)

Return: CF set on error
       AH = status (see #0446)

(Table 0447)
Values for pointing device resolution:
 00h   one count per mm
 01h   two counts per mm
 02h   four counts per mm
 03h   eight counts per mm