Int 83 Fn 04  - Jm Pro Tracker V5.0 - Set Dma Buffer???                    [s]

   AH = 04h
   CX = number of bytes in suggested buffer
   ES:DI -> suggested buffer for DMA transfers???

Return: CF clear if successful
       ES:AX -> actual buffer (filled with bytes of 80h)
       CX = actual length (multiple of 4)
   CF set on error
       AX = error code (see #3647)

Note:  the buffer must not cross a 64K DMA page boundary