I/O Resource Usage Reduction
Microsoft has implemented support to help reduce the dependence that PCI, PCI-X, and PCI Express devices have on the usage of input/output (I/O) space addresses that are accessed by the I/O base address registers (BARs). The number of I/O resources used on a personal computer has continued to increase over the years. This I/O resource usage on PCI, PCI-X, and PCI Express buses is increasingly becoming a cause of resource contention problems. These problems are expected to become worse for systems using PCI Express buses, compared to those using PCI and PCI-X buses, due to the number of virtual PCI-to-PCI bridges that are used in both client and server systems. It is therefore becoming more necessary to transition hardware designs away from reliance on I/O resources and onto using memory resources, which are much more plentiful. For more information on how device manufacturers, driver developers, firmware engineers, and system manufacturers can disable unused I/O BARs and reduce or eliminate the amount of I/O space used in a computer, refer to the I/O Resource Usage Reduction white paper.
To reduce I/O resource usage, the driver developer must place the following entry in the device driver's INF file.
[DDInstall.HW] Include=pci.inf Needs=PciIoSpaceNotRequired.HW