I/O Address ReMapping

Because HT does not directly support I/O address space, it reserves a 32MB of memory address space for transporting I/O addresses across the bus. When the processor initiates and I/O transaction, the address must be translated by the CPU to HT bridge to an address within the reserved HT I/O address range (FD_FC00_0000h- FD_FDFF_FFFFh). HT transports the transaction across the HT chain to the HT-to-PCI bridge which must translate the HT I/O address so that is falls within the expansion bus I/O address range.

The IO Size register within the Address Remapping Capability block supports the I/O address space remapping. This 5-bit register defines the size of the I/O address space on the expansion bus, up to 32MBs. Note that the ...

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