HelpPC 2.10 Quick Reference Utility Copyright 1991 David Jurgens

                Intel Defined CPU Exception Table (see notes)

       Interrupt         Function

        0      Divide by zero
        1      Single step
        2      Non-maskable  (NMI)
        3      Breakpoint
        4      Overflow trap
        5      BOUND range exceeded (186,286,386)
        6      Invalid opcode (186,286,386)
        7      Coprocessor not available (286,386)
        8      Double fault exception (286,386)
        9      Coprocessor segment overrun (286,386)
        A      Invalid task state segment (286,386)
        B      Segment not present (286,386)
        C      Stack exception (286,386)
        D      General protection exception (286,386)
        E      Page fault (286,386)
        F      Reserved
       10      Coprocessor error (286,386)

            IBM PC Hardware Interrupt Table (in order of priority)

       IRQ#  Interrupt         Function

       IRQ0     8      timer (55ms intervals, 18.2 per second)
       IRQ1     9      keyboard service required
       IRQ2     A      slave 8259 or EGA/VGA vertical retrace
       IRQ8    70      real time clock  (AT,XT286,PS50+)
       IRQ9    71      software redirected to IRQ2  (AT,XT286,PS50+)
       IRQ10   72      reserved  (AT,XT286,PS50+)
       IRQ11   73      reserved  (AT,XT286,PS50+)
       IRQ12   74      mouse interrupt  (PS50+)
       IRQ13   75      numeric coprocessor error  (AT,XT286,PS50+)
       IRQ14   76      fixed disk controller (AT,XT286,PS50+)
       IRQ15   77      reserved  (AT,XT286,PS50+)
       IRQ3     B      COM2 or COM4 service required, (COM3-COM8 on MCA PS/2)
       IRQ4     C      COM1 or COM3 service required
       IRQ5     D      fixed disk or data request from LPT2
       IRQ6     E      floppy disk service required
       IRQ7     F      data request from LPT1 (unreliable on IBM mono)

              Interrupt Table as Implemented by System BIOS/DOS

     INT #   Locus             Function

        0      CPU     divide by zero
        1      CPU     single step
        2      CPU     non-maskable
        3      CPU     breakpoint
        4      CPU     overflow trap
        5      BIOS    print screen
        6      CPU     Invalid opcode (186,286,386)
        7      CPU     coprocessor not available (286,386)
        8      IRQ0    timer (55ms intervals, 18.21590 per second)
        9      IRQ1    keyboard service required (see INT 9)
        A      IRQ2    slave 8259 or EGA/VGA vertical retrace
        B      IRQ3    COM2 service required (PS/2 MCA COM3-COM8)
        C      IRQ4    COM1 service required
        D      IRQ5    fixed disk or data request from LPT2
        E      IRQ6    floppy disk service required
        F      IRQ7    data request from LPT1 (unreliable on IBM mono)
       10      BIOS    video (see INT 10)
       11      BIOS    Equipment determination (see INT 11)
       12      BIOS    memory size (see INT 12)
       13      BIOS    disk I/O service  (see INT 13)
       14      BIOS    serial communications (see INT 14)
       15      BIOS    system services, cassette (see INT 15)
       16      BIOS    keyboard services (see INT 16)
       17      BIOS    parallel printer (see INT 17)
       18      BIOS    ROM BASIC loader
       19      BIOS    bootstrap loader (unreliable, see INT 19)
       1A      BIOS    time of day     (see INT 1A)
       1B      BIOS    user defined ctrl-break handler (see INT 1B)
       1C      BIOS    user defined clock tick handler (see INT 1C)
       1D      BIOS    6845 video parameter pointer
       1E      BIOS    diskette parameter pointer (base table)
       1F      BIOS    graphics character table
       20      DOS     general program termination
       21      DOS     function request services (see INT 21)
       22      DOS     terminate address (see INT 22)
       23      DOS     control break termination address (see INT 23)
       24      DOS     critical error handler (see INT 24)
       25      DOS     absolute disk read (see INT 25)
       26      DOS     absolute disk write (see INT 26)
       27      DOS     terminate and stay resident (see INT 27)
       28      DOS     idle loop, issued by DOS when idle (see INT 28)
       29      DOS     fast TTY console I/O (see INT 29)
       2A      DOS     critical section and NETBIOS (see INT 2A)
       2B      DOS     internal, simple IRET in DOS 2.0-5.0
       2C      DOS     internal, simple IRET in DOS 2.0-5.0
       2D      DOS     internal, simple IRET in DOS 2.0-5.0
       2E      DOS     exec command from base level command
                       interpreter     (see INT 2E)
       2F      DOS     multiplexer (see INT 2F)
       30-31   CPM     far jump vector for CPM (not an interrupt)
       31      DPMI    DOS Protected Mode Interface (for DOS extenders)
       32              reserved
       33              mouse support (see INT 33)
       34-3E           Microsoft/Borland floating point emulation
       3F              overlay manager
       40      BIOS    hard disk
       41      BIOS    fixed disk 0 parameters pointer (see INT 13,9)
       42      BIOS    relocated video handler (EGA/VGA/PS)
       43      BIOS    user font table (EGA/VGA/PS)
       44      BIOS    first 128 graphics characters (also Netware)
       45      BIOS    reserved for BIOS
       46      BIOS    fixed disk 1 parameters ptr (see INT 13,9/INT 41)
       47      BIOS    reserved for BIOS
       48      BIOS    PCjr cordless keyboard translation
       49      BIOS    PCjr non-keyboard scancode translation table
       4A      BIOS    user alarm  (AT,CONV,PS/2) (see INT 4A)
       4B-4F   BIOS    reserved
       50      BIOS    periodic alarm from timer (PS/2)
       51-58   BIOS    reserved
       59      BIOS    GSS Computer Graphics Interface
       5A      BIOS    cluster adapter BIOS entry point
       5B      BIOS    cluster adapter boot
       5C      NETBIOS NETBIOS interface, TOPS interface
       5D-5F   BIOS    reserved for BIOS
       60-67           reserved for user software interrupts
       67      EMS     LIM/EMS specification (see INT 67)
       68              APPC
       69-6B           reserved by IBM
       6C      DOS     DOS 3.2 real time clock update
               BIOS    system resume vector
       6D-6F           reserved
       70      IRQ8    real time clock  (AT,XT286,PS50+, see INT 15)
       71      IRQ9    software redirected to IRQ2     (AT,XT286,PS50+)
       72      IRQ10   reserved  (AT,XT286,PS50+)
       73      IRQ11   reserved  (AT,XT286,PS50+)
       74      IRQ12   mouse interrupt  (PS50+)
       75      IRQ13   numeric coprocessor NMI error  (AT,XT286,PS50+)
       76      IRQ14   fixed disk controller (AT,XT286,PS50+)
       77      IRQ15   reserved  (AT,XT286,PS50+)
       78-79           unused
       80-85           ROM BASIC
       86-F0   DOS     reserved for BASIC interpreter use
       86      NETBIOS NETBIOS relocated INT 18
       E0      CPM     CP/M 86 function calls
       F1-FF           reserved by IBM
       FE-FF           may be destroyed by return from protected
                       mode using VDISK on 286 machines (Apr 86, DDJ)

       - Intel defined 0 through 20h for use for internal CPU;  IBM
         redefined interrupts 0 through 1Fh for its own use, hence
         the duplicate definitions in the tables
       - all interrupts except the internal CPU exceptions push the
         flags and the CS:IP of the next instruction onto the stack.
         CPU exception interrupts are similar but push the CS:IP of the
         causal instruction.   8086/88 divide exceptions are different,
         they return to the instruction following the division
       - interrupts are disabled upon entry into any interrupt routine and
         should be enabled by the user or by an IRET
       - in DOS 3.2+ hardware IRQ interrupts are re-vectored through DOS
         to provide standard stack frames

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