AST RESEARCH TECHNICAL BULLETIN TB-0030                   7-17-84
    

           DMA CHANNEL ASSIGNMENT IN THE IBM PC AND XT


When  interfacing products to the IBM PC or XT,  which use Direct 
Memory Access (DMA),  it is necessary to insure that there is not 
a conflict with a device using the same channel.

The following table shows the channels and their assignments.


                                                     ADD-ON
     CHANNEL              IBM ASSIGNMENT           ASSIGNMENT


      DMA 0             IBM MEMORY REFRESH      NONE

      DMA 1             IBM - SDLC              AST-PCOX - STD
                                                AST-PCNET

      DMA 2             IBM - FLOPPY DISK       NONE

      DMA 3             IBM - HARD DISK         AST-PCOX (Alt.)
                                                OTHER HARD DISK