IRQ Steering is feature in Win95 OSR2 and Win98 that allows Windows to dynamically assign IRQs to PCI hardware devices.  
This capability does not work with older ISA hardware
.

This Microsoft article contains more background information on IRQ Steering.

 

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You can tell if you are using IRQ steering  by opening the Device Manager in the System Control Panel.  You then double click on the Computer icon to get a list of IRQ assignments for your computer.

If you see entries like the circled ones below, you’re using IRQ steering. .

Sometimes IRQ steering causes problems rather than solves them and you may have to disable it and assign IRQs manually. However, you may first have to free up IRQs by disabling and probably physically removing unneeded devices.

Open Device Manager (double click on the System Control Panel) and click on the “+” sign next to System Devices to expand it.  Double click on the PCI bus icon as shown below.

The PCI bus properties window will open.  Disable IRQ Steering by unchecking the “Use IRQ Steering” box.

Newer computers with ACPI compliant BIOSes and running Win98 have more options for controlling IRQ steering.  You may need to experiment with the settings in IRQ steering Properties.  Try leaving IRQ Steering enabled, but first uncheck the Get IRQ table using ACPI BIOS selection.

Use the ? help (click on the ? in the window top right hand corner, then click on the item that you want an explanation for) to guide you in your experimentation!