Efficiently controlling special memory mapped system accesses

In one embodiment, an input/output memory management unit (IOMMU) comprises a control register configured to store a base address of a set of translation tables and control logic coupled to the control register. The control logic is configured to respond to an input/output (I/O) device-initiated request having an address within an address range of an address space corresponding to a peripheral interconnect. One or more operations other than a memory operation are associated with the address range, and the control logic is configured to translate the address to a second address outside of the address range if the translation tables specify a translation from the address to the second address, whereby a memory operation is performed in response to the request instead of the one or more operations associated with the address range.