    =

    AST RESEARCH, INC.            TECHNICAL BULLETIN # 1033               12-14-94

    =

                       PLUG-N-PLAY SYSTEMS AND ISACU IRQ 2 CONFLICT

    PROBLEM:        The AST ISACU does not allow the use of IRQ 2(9) on
                    Plug-n-Play systems. The system returns a resource conflict
                    error message.

    CAUSE:          IRQ2 is used by the interrupt controller on the system board
                    and it is not available.

    SYSTEMS
    AFFECTED:       All Plug-n-Play systems.

    SOLUTION:       When installing a non-Legacy ISA adapter board in a
                    Plug-n-Play system that requires IRQ 2(9), select IRQ 9(2) in
                    the ICU program.  (Legacy refers to any ISA board which is not
                    designed to support Plug-n-Play.)  Follow the steps below:

                    1) Add in a VGA adapter to the system to disable the integrated
                       VGA adapter.

                    2) Run the ICU utility.  Since the integrated VGA is no longer
                       installed, IRQ2 (shown as 9(2) in the ICU utility) is now
                       available.  (Because IRQ 2 is used as a cascade to IRQ 9,
                       the system board will always show 2(9) in use.  The same
                       interrupt will be available to the user as 9(2).)  Configure
                       the  desired legacy board for IRQ2 (the Token Ring adapter
                       configuration file will display interrupts as IRQx while
                       the resources list will display it as 9(2))and save the
                       configuration.

                    3) Remove the add-in VGA card and restart the system.  Since
                       IRQ2 is now configured for another board, the integrated
                       VGA adapter will select another IRQ.  (If it is desired
                       that the VGA use a specific IRQ, the user can install
                       phantom ISA adapters which use all interrupts except the
                       one desired for the VGA adapter.  When the system is
                       restarted, the integrated VGA adapter will then select from
                       among the remaining interrupts to configure itself.)

                    4) Run ICU again.  Inspect the new settings.  If the same
                       setting will be required for multiple systems, save the
                       current configuration under the Advanced menu item to a
                       file.  Save the configuration and quit the utility.  (This
                       file can be used by copying it to other systems and reading
                       it in directly through the Advanced menu item, rather than
                       using the first 3 steps listed above.)