Microsoft KB Archive/196123

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PRB: Windows 98: PCMCIA Memory Windows May Fail Below 1 MB

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Q196123

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The information in this article applies to:


 * Microsoft Win32 Device Driver Kit (DDK) Windows 98

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SYMPTOMS
Under Windows 98, PCMCIA devices used with Texas Instruments (TI) 113x CardBus controllers may fail to receive memory windows below 1 megabyte (MB). Specifying a specific configuration tuple memory address below 1 MB does not work, nor does using an .inf file override to force the window below 1 MB.

CAUSE
TI 113x CardBus controllers can only address memory windows that are mapped into a single 16-MB frame. Windows 95 OSR2 maps this 16-MB frame to the low 16 MB of physical memory, meaning that all memory windows must reside below 1 MB because systems usually have at least 16 MB of RAM.

However, Windows 98, by default, maps the 16-MB frame above the top of physical memory, meaning that memory windows must also reside above system RAM.

RESOLUTION
In Windows 98, Cbss.vxd uses a registry entry to override the default TI 113x 16-MB frame mapping location. If the registry location below contains an entry of any name with a value of 2, CBSS maps the controller's 16-MB frame to the low 16 MB of physical memory, just as Windows 95 OSR2 does:

  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\CBSS\Hacks This allows memory windows to be mapped below 1 MB.

You can use the following line in an AddReg section in the .inf file to force this behavior:

  HKLM,System\CurrentControlSet\Services\VxD\CBSS\ Hacks,TIForceLow,3,02, 00,00,00 NOTE: This line should not include any breaks in your .inf file.

NOTE: The value name TIForceLow is arbitrary. Any name works successfully.

STATUS
This behavior is by design.

Additional query words:

Keywords : kbDDK kbOSWin98

Issue type : kbprb

Technology : kbAudDeveloper kbWin98search kbWinDDKSearch kbWin32sSearch kbWin32DDKSearch kbWin32DDK98