INFO: Use and Importance of DMA32BitAddresses (282873)


The information in this article applies to:

  • Microsoft Windows 95 Driver Development Kit (DDK)
  • Microsoft Windows 98 Driver Development Kit (DDK)
  • Microsoft Windows ME Driver Development Kit (DDK)
This article was previously published under Q282873

SUMMARY

This articles discusses the use and importance of DMA32BitAddresses.

MORE INFORMATION

SCSI MiniPort (ScsiPort) drivers, written for disk controllers, use the PORT_CONFIGURATION_INFORMATION structure to fill in adapter specific information in response to a HwFindAdapter routine call back.

The HwFindAdapter call back function is called when a driver calls ScsiPortInitialize.

It is very important for a ScsiPort driver to set the Dma32BitAddresses flag to TRUE. Failing to do so results in the Bigmem.vxd file being loaded and inserted in the call down stack.

The Bigmem.vxd file is provided by the system to help some legacy ISA controllers that can not handle memory above 16 megabytes. The Bigmem.vxd file performs a lot of memory mapping and degrades overall system performance.
Modification Type:MinorLast Reviewed:3/9/2005
Keywords:kbinfo kbSCRAPKeep KB282873
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