Microsoft KB Archive/195317

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PRB: Filtering of PCMCIA Device IRQ Request Mask

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Q195317

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The information in this article applies to:


 * Microsoft Win32 Device Driver Kit (DDK) Windows 95

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SYMPTOMS
PCMCIA devices might appear to be unable to use all the possible IRQs specified in the device's BASIC_LOG_CONF IRQ Request Mask. For example, the BASIC_LOG_CONF IRQ Request Mask might specify FFFF, but the FILTERED_LOG_CONF and ALLOC_LOG_CONF will likely show a value other than FFFF, which limits the range of possible IRQs for the device.

CAUSE
The Windows socket driver walks through and tests all 16 IRQs and writes an entry in the software section of the registry for the socket (HKLM\System\CurrentControlSet\Services\Class\PCMCIA\XXXX) named IRQMask. if the registry entry already exists, the socket driver does not go through this process. This IRQMask is used to filter the BASIC_LOG_CONF IRQ Request Mask. The filtering is dependent upon IRQ usage by other devices in the system. The filtering is not affected by tuple data or INF overrides.

STATUS
This behavior is by design.