Error Code 29 After Resuming from Suspend Mode

• Microsoft Windows 95 OEM Service Release version 2.5

SYMPTOMS

After you resume your computer from Suspend mode, a Peripheral Component Interconnect (PCI) device may appear in Device Manager with an exclamation point in a yellow circle. When you view the properties of the PCI device, the following message may be displayed under Device Status:

   The device has been disabled in the hardware. In order to use this
   device, you must re-enable the hardware. See your hardware
   documentation for details. (Code 29.) 

CAUSE

This problem occurs because Windows 95 OEM Service Release 2.5 does not rebalance interrupt request lines (IRQs) correctly.

RESOLUTION

To work around this problem, remove or disable an unused device in Device Manager to free a system IRQ. To disable a device in Device Manager, follow these steps:

1. Click Start, point to Settings, and then click Control Panel.



2. Double-click System.



3. On the Device Manager tab, double-click the branch containing the device you want to disable, click the device, and then click Properties.



4. On the General tab, click the Disable In This Hardware Profile check box to select it, and then click OK.



5. Click Close, and then restart your computer.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Windows 95 OEM Service Release 2.5.

This problem is fixed in Microsoft Windows 98.

MORE INFORMATION

When the computer is started, Windows 95 performs a PCI IRQ rebalance to free up system IRQs as needed. In order to accomplish this task, Windows 95 routes multiple PCI interrupts to a single system interrupt.

Internal data structures in Windows 95 are set up to maintain information on which PCI IRQs are routed to which system IRQs. In cases where multiple PCI interrupts are routed to a single system interrupt, the pointer to this IRQ routing information may be lost. Windows 95 continues to function properly until the computer goes into Suspend mode. At that time, Configuration Manager attempts to remove resources for all PCI devices. It cannot do so on the device or devices that use the PCI interrupt controlled by the missing IRQ routing data structure, resulting in that PCI device having an error code 29 (CM_PROB_HARDWARE_DISABLED).

Due to the nature of PCI interrupts and IRQ routing, this problem may or may not be evident on a given computer based on a number of variables, including PCI slot design (how the PCI interrupts are routed between slots), PCI card interrupt usage, and system IRQ availability.

For additional information about PCI bus IRQ steering, please see the following article in the Microsoft Knowledge Base:

Q182604 Description of PCI Bus IRQ Steering

Keywords : kbenv kberrmsg osr2
Version : WINDOWS:95
Platform : WINDOWS
Issue type : kbprb