Int 31 Fn 0304  P - Dpmi 0.9+ - Free Real Mode Callback Address            [E]

   AX = 0304h
   CX:DX = real mode callback address

Return: CF clear if successful
   CF set on error
       AX = error code (DPMI 1.0+) (8024h) (see #2814)

Note:  the limited DPMI host built into Phar Lap's 286|DOS-Extender v2.5 does
     not support this function

See Also: AX=0303h