AST RESEARCH TECHNICAL BULLETIN TB-0034                   7-18-84


       HARDWARE INTERRUPT ASSIGNMENT IN THE IBM PC AND XT


When interfacing products to the IBM PC or XT, which use hardware 
interrupts,  it is necessary to insure their is not conflict with 
other devices in the system utilizing the same interrupt.

The  following  table  shows the hardware  interrupts  and  their 
assignments.


  INTERRUPT           IBM ASSIGNMENT           ADD-ON ASSIGNMENT

   IRQ NMI                PARITY                    NONE

   IRQ 0                  TIMER                     NONE

   IRQ 1                 KEYBOARD                   NONE

   IRQ 2                 RESERVED              AST-SNA, AST-BSC,
                                               AST-3780, AST-5251
                                               AST-PCNET

   IRQ 3                  COM 2                AST COM 2, AST-SNA
                         IBM-SDLC              AST-BSC, AST-3780,
                    IBM-BSC  (Secondary)       AST-5251, AST-PCNET
  
   IRQ 4                  COM 1                AST COM 1, AST-SNA
                         IBM-SDLC              AST-BSC, AST-3780
                     IBM-BSC (Primary)         AST-5251, AST-PCNET

   IRQ 5               IBM-HARD DISK           SAME AS IRQ 2

   IRQ 6              IBM-FLOPPY DISK          AST-SNA, AST-BSC
                                               AST-3780, AST-5251

   IRQ 7                  PRINTER              SAME AS IRQ 6