Windows 2000 and Windows XP claim IRQ-6 settings even if floppy disk controllers are not present

Windows 2000 and Windows XP may claim IRQ-6 settings that are usually reserved for floppy disk controllers. This issue occurs even if the floppy disk controller is unavailable in the basic input/output system (BIOS), or the floppy disk drive has been physically removed.

If you remove the standard floppy disk controller in Device Manager and restart the computer, the Windows 2000 Plug and Play process may detect and install a floppy disk controller even if the device is unavailable in the BIOS, or if the floppy disk drive has been physically removed from the computer.

If you disable the floppy disk controller in Device Manager, and then click the Resources tab in System properties, you may receive the following message: If you use the Computer Management tool in Control Panel, click System Information, click Hardware Resources and then click IRQs to view the resources, the IRQ-6 setting is not reported to be claimed. However, if you attempt to configure another Industry Standard Architecture (ISA) device to use an IRQ-6 setting, you receive a message that states that the resource is already in use.

This issue can occur because in non-ACPI-based systems that use a Plug and Play BIOS, Ntdetect.com always reports a device node for the floppy disk controller on x86-based systems.

For ACPI-based systems, Acpi.sys enumerates floppy disk controllers from BIOS tables that are exported to the operating system; only devices that are present are reported in this file.

To resolve this issue, update your system BIOS to an ACPI-compliant BIOS. If you are already using an ACPI-based BIOS, modify the system BIOS so that it does not report a floppy disk controller when the controller is unavailable. Contact your system manufacturer for a BIOS update.

If the BIOS is an ACPI-based BIOS, when you remove the pnp0700 device node from the ACPI tables, a floppy disk should not be reported.

Note If you are using a working ACPI-based BIOS, the Plug and Play BIOS device node tables can be safely ignored. Even if pnp0700 is removed from the Plug and Play BIOS tables, only the ACPI tables are checked.

To meet reliability goals, Windows 2000 always claims the IRQ-6 setting on non-ACPI-based BIOS systems. Some chipsets do not properly release resources that are associated with an unavailable floppy disk controller. This behavior may cause Windows to stop responding (hang); it may also cause memory corruption, or other Plug and Play resource issues.

Windows 2000 does not claim the IRQ-6 setting if the system meets the "legacy-free" specification and implements legacy-free tables in the system BIOS, or if the BIOS is fully ACPI-complaint.

For more information about legacy-free hardware and BIOS specifications, visit the following Microsoft Web site: