Microsoft KB Archive/170324

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CMD PCI-0646U Accessed in Compatibility Mode in OSR2


The information in this article applies to:

  • Microsoft Windows 95 OEM Service Release, versions 2, 2.1


When you use an IDE controller based on the CMD PCI-0646U chip set in Windows 95 OEM Service Release 2 or 2.1 (OSR2), the controller is not recognized, protected-mode drivers are not loaded, and the controller is accessed in Compatibility (BIOS) mode.


The CMD PCI-0646U chip set uses some control registers in a different manner from earlier models of CMD controllers. The Windows PCI driver accesses these registers in a way that causes it not to recognize this controller.


This issue is resolved by the following updated file for Windows 95 OSR2, and later versions of this file:

   PCI.VXD  version 4.00.1119  dated 7/25/97  42,271 bytes 


Microsoft has confirmed this to be a problem in Microsoft Windows 95 OEM Service Release 2 (OSR2). An update to address this problem is now available, but is not fully regression tested and should be applied only to computers experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft does not recommend implementing this update at this time. Contact Microsoft Technical Support for additional information about the availability of this update.

This issue is resolved in Microsoft Windows 98.


For additional information about issues resolved by updates to this component, please see the following articles in the Microsoft Knowledge Base:

Q182591 CardBus Cards Not Enumerated on Some PC Card Controllers

Q173677 Audio Problems with Cirrus Logic PD6832 CardBus Controller

Q164873 PCI Device Not Configured and Resources Unassigned

Q164222 CardBus Card in Docking Station May Not Be Configured

Q163938 Inserting Multifunction PC Card May Hang Computer

Q159543 Intel ProShare PC Card May Hang Computer

Q159492 PC Card Device Not Enumerated When Reinserted

For additional information about Windows 95 updates, please see the following article in the Microsoft Knowledge Base:

Q161020 Implementing Windows 95 Updates

Additional query words: 95 chipset

Keywords : kbhw osr2 win95
Issue type : kbprb
Technology : kbWin95search kbOPKSearch kbWin95OPKOSR2 kbWin95OPKOSR210

Last Reviewed: January 31, 2001
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