Resolving resource conflicts
Anyone who remembers IRQ conflicts will be thankful that
current computers support ACPI BIOS. With ACPI BIOS, resources are allocated automatically by
the operating system at startup, and multiple devices can share the
same IRQ settings. These changes mean IRQ conflicts are
largely a thing of the past. However, ACPI depends on Plug and Play,
and devices that are not fully compatible can sometimes cause
problems, particularly legacy ISA devices.
If you suspect a device conflict is causing a problem with the
current device, check the Conflicting Device list in the lower portion of the
Resources tab. It will either list No Conflicts or the
specific source of a known conflict. In Device Manager, you can
quickly check resource allocations by choosing Resources By Type or
Resources By Connection on the View menu.
In Figure 15, both ISA and
PCI devices are using IRQ settings. You’ll note each ISA device has a
separate IRQ setting, while multiple PCI devices share the same IRQ
settings. This is very typical. Note also that the PCI Modem device
has a question mark as an icon. This is because the device isn’t
configured properly, not because there’s a conflict. In this
example, there are no conflicts.
Figure 15. View resources by type or resources by connection to check
resource settings in Device Manager.
Another way to check for conflicts is to use the System
Information utility (Msinfo32.exe). In Server Manager, select System
Information on the Tools menu. In System Information, expand
Hardware Resources, and then select Conflicts/Sharing.
As shown in Figure 16, a list of all
resources that are in use is displayed. Again, keep in mind that
devices can share IRQ settings thanks to ACPI, so what you are
looking for are two unrelated devices sharing the same memory
addresses or I/O ports, which would cause a conflict. Keep in mind
related devices can share memory addresses and I/O ports. In the
example, the PCI Express Root Complex shares the same I/O port as
the Direct Memory Access Controller and the Mobile Express Root Port
shares the same memory addresses as the Basic Display Adapter
resources. That’s okay because this is typical and not
causing an issue.
Figure 16. Use System Information to check for resource
You can try to resolve resource conflicts in several ways. Some devices use
jumpers to manage resource settings, and in this case, the operating
system cannot control the resource settings. To make changes, you
must shut down the computer, remove the device, change the
jumper settings, and then replace the device. In some
cases, the jumpers are managed through software rather than an
actual jumper switch. Here, you would use the device setup or
configuration utility to change the resource settings.
For PCI devices, you can try swapping the cards between PCI
slots. This will help if the IRQ or other resource settings are
assigned on a per-slot basis, as is the case with some motherboards.
You might be able to check the motherboard documentation to see
which IRQ interrupts are assigned to which slots. In any case, you
need to experiment to see which card configuration works.
For PCI devices, a conflict could also be caused by the device
driver and the way it works with the ACPI BIOS. You should check to
see whether an updated device driver and a BIOS update are
available. Installing one or both should resolve the
As a last resort, you can change the resource settings manually for some devices in Device
Manager. In the Resources tab, select the resource type that you
want to work with. If you can make a change, you should be able to
clear the Use Automatic Settings check box and then see whether any
of the alternate configurations in the Setting Based On box resolve
the conflict. Keep in mind that you are now manually managing the resource settings. To allow the Windows operating
system again to manage the settings automatically, you must select
the Use Automatic Settings check box.