Microsoft KB Archive/169579

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PRB: PCMCIA Memory Window Size Limitations

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Q169579

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The information in this article applies to:


 * Microsoft Win32 Device Driver Kit (DDK) Windows 95

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SYMPTOMS
Windows 95 may not successfully allocate large memory windows to PCMCIA cards on machines containing 16MB or more of RAM.

CAUSE
PCMCIA devices are subject to the ISA bus address restriction of 20 bits or 16MB. If a machine has at least 16MB of RAM, the PCMCIA memory window must then reside between 640KB - 1MB.

Depending on the machine configuration, Windows 95 may not be able to provide large PCMCIA memory windows. For example, on many machines memory windows of 64KB or larger may fail. Even smaller windows may fail depending on the machine configuration.

RESOLUTION
It may be advantageous to create multiple logical configurations, each with a progressively smaller memory window all the way down to 4KB. The driver can then take advantage of the larger memory window if it is available, and can still work even if only a small memory window can be allocated.

MORE INFORMATION
See the Windows 95 DDK for more information on PCMCIA.

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Issue type :

Technology : kbAudDeveloper kbWin95search kbWinDDKSearch kbWin32sSearch kbWin32DDK95 kbWin32DDKSearch