Addressing
When this bit is cleared, the 41210 forwards transactions addressing the VGA frame buffer memory and VGA I/O registers from PCI Express* to PCI when the defined memory and I/O address ranges enable forwarding. When cleared, accesses to the VGA frame buffer memory are forwarded from PCI to PCI Express* when the defined memory address ranges enable forwarding. However, the master enable bit must still be set. The VGA I/O addresses are never forwarded to PCI Express* when the upstream I/O enable bit in BINIT register is cleared. When this bit is set and also the VGA enable bit is set, the 41210 does not forward the VGA I/O addresses from PCI to PCI Express*.
The VGA frame buffer consists of the memory address range 000A
The VGA I/O addresses consist of the I/O addresses
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50 | Intel® 41210 Serial to Parallel PCI Bridge Developer’s Manual |