Operating System Does Not Recognize That the Secondary Channel Has Been Disabled (272586)

SYMPTOMS

When you run Windows 2000 on a computer that is using a VIA Integrated Device Electronics (IDE) controller chipset, if you disable the secondary channel in the BIOS, the operating system does not recognize that the secondary is disabled. As a result, Device Manager continues to report that the second channel is enabled and an interrupt is allocated to the channel, even though the devices on the channel are not recognized by the operating system.

CAUSE

Windows 2000 does not completely support the VIA chipset and does not know how to correctly query the status of the IDE channels. Therefore, it sets the status of both channels to Enabled, by default. This behavior does not affect the functionality of the chipset. When all channels are enabled, the chipset works properly. However, a user cannot disable the secondary channel to reclaim the interrupt that the channel is using.

RESOLUTION

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

WARNING: You should only follow the procedure to resolve this issue if your computer has a VIA IDE chipset (model numbers 686A, 686B and 596). To verify that you are using this device, start the System tool in Control Panel, click the Hardware tab, and then click Device Manager. If you are using the VIA IDE chipset, the following driver is listed in the IDE/ATAPI Controllers branch:

Via Bus Master IDE Controller

To resolve this issue, follow these steps:

Start Registry Editor (Regedit.exe or Regedt32.exe).
Locate and click the following registry key:

NOTE: The last value is longer than the value listed in the following registry key, but the first eight characters are 4D36E96A.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A...}
Click the 0000, 0003 and 0006 keys, and add the following values on each key:
- Value: MasterOnConfigOffset
  Type: REG_DWORD
  DWORD Value: 0x40
- Value: MasterOnMask
  Type: REG_DWORD
  DWORD Value: 0x02
- Value: SlaveOnConfigOffset
  Type: REG_DWORD
  DWORD Value: 0x40
- Value: SlaveOnMask
  Type: REG_DWORD
  DWORD Value: 0x01
Restart the computer.

The operating system should now display the BIOS settings of the IDE channels in Device Manager. If any of the channels have been disabled, the resources that are being used by that channel are released so that they can be used by other devices.