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Memory-mapped I/O is preferred in IA-32 and x86-64 based architectures because the instructions that perform port-based I/O are limited to one register: EAX, AX, and AL are the only registers that data can be moved into or out of, and either a byte-sized immediate value in the instruction or a value in register DX determines which port is the source or destination port of the transfer.
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 ...
One of the major improvements the PCI Local Bus had over other I/O architectures was its configuration mechanism. In addition to the normal memory-mapped and I/O port spaces, each device function on the bus has a configuration space, which is 256 bytes long, addressable by knowing the eight-bit PCI bus, five-bit device, and three-bit function numbers for the device (commonly referred to as the ...
In contrast, in direct memory access (DMA) operations, the CPU is uninvolved in the data transfer. The term can refer to either memory-mapped I/O (MMIO) or port-mapped I/O (PMIO). PMIO refers to transfers using a special address space outside of normal memory, usually accessed with dedicated instructions, such as IN and OUT in x86 architectures.
When it attempts to access memory, the MMU reads the segment number from the processor's memory bus, finds the corresponding entry for that program in its internal memory, and expresses the mapped version of the value on the memory's bus while the lower bits of the original address are passed through unchanged.
WASHINGTON (Reuters) -The U.S. government posted a $367 billion budget deficit for November, up 17% from a year earlier, as calendar adjustments for benefit payments boosted outlays by some $80 ...
Memory-mapped I/O, an alternative to port I/O; a communication between CPU and peripheral device using the same instructions, and same bus, as between CPU and memory Virtual memory , technique which gives an application program the impression that it has contiguous working memory, while in fact it is physically fragmented and may even overflow ...
Elon Musk said Starlink satellite internet is inactive in India, his first comments since authorities seized two of the company's devices in recent weeks, one in an armed conflict zone and another ...