Mac DOS: Hardware Interrupts Used by Common Devices (37928)


The information in this article applies to:

  • Microsoft Mail for AppleTalk Networks, MS-DOS workstation 3.0
  • Microsoft Mail for AppleTalk Networks, MS-DOS workstation 3.1
This article was previously published under Q37928

SYMPTOMS

Interrupts are the means by which the computer's circuitry outside the central processor reports that something (such as a keystroke) has occurred and requests that some action be taken. Serious problems may occur if two devices installed in a computer are using the same interrupt; for example, one of the devices may be disabled, or your computer system may stop responding (hang) because the computer cannot service two interrupts at one time. This problem may occur when you try to install an AppleTalk network card for use with Microsoft Mail (MS-DOS client).

RESOLUTION

To resolve an interrupt conflict, set one of the devices to use another interrupt (if possible), or remove one of the devices from your hardware configuration.

MORE INFORMATION

The following is a table of hardware interrupts used by the IBM PC/XT or PC/AT and common devices: 
   Interrupt    Potential Use
   ---------    -------------

    0           System board timer

    1           Keyboard

    2           PC/AT hard disk*, bus mouse, some clock calendars, UBNET
                cards (on PC/XTs), Apple LocalTalk, or TOPS FlashCard
                network cards

    3           Serial port 2, bus mouse, Apple LocalTalk, TOPS FlashCard,
                or MacBridge ATB network cards

    4           Serial port 1, bus mouse, Apple LocalTalk network card

    5           PC/XT hard disk, bus mouse, UBNET card (on PC/ATs)

    6           Floppy disk controller

    7           Parallel port 1

IBM PC/AT Only

    8           Real-time clock

    9           Software redirect to IRQ2

   10-12        Reserved

   13           Coprocessor

   14           Hard disk controller

   15           Reserved
* The IBM PC/AT uses IRQ2 to access interrupts 8-15 by activating a separate interrupt controller.
Modification Type:MajorLast Reviewed:5/20/2003
Keywords:KB37928
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