Input–output memory management unit

Common card · No. 318500

In computing, an input–output memory management unit (IOMMU) is a memory management unit (MMU) connecting a direct-memory-access–capable (DMA-capable) I/O bus to the main memory. Like a traditional MMU, which translates CPU-visible virtual addresses to physical addresses, the IOMMU maps device-visible virtual addresses (also called device addresses or memory mapped I/O addresses in this context) to physical addresses. Some units also provide memory protection from faulty or malicious devices. An example IOMMU is the graphics address remapping table (GART) used by AGP and PCI Express graphics cards on Intel Architecture and AMD computers. On the x86 architecture, prior to splitting the functionality of northbridge and southbridge between the CPU and Platform Controller Hub (PCH), I/O virtualization was not performed by the CPU but instead by the chipset.

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