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Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU). [ 1 ] Without DMA, when the CPU is using programmed input/output , it is typically fully occupied for the entire duration of the read or write operation, and is thus ...
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 ...
In computing, remote direct memory access (RDMA) is a direct memory access from the memory of one computer into that of another without involving either one's operating system. This permits high-throughput, low- latency networking, which is especially useful in massively parallel computer clusters .
The Ultra DMA (Ultra Direct Memory Access, UDMA) modes are the fastest methods used to transfer data through the ATA hard disk interface, usually between a computer and an ATA device. UDMA succeeded Single / Multiword DMA as the interface of choice between ATA devices and the computer.
DMA is included in a number of connections, because it lets a connected device (such as a camcorder, network card, storage device or other useful accessory or internal PC card) to transfer data between itself and the computer at the maximum speed possible, by using direct hardware access to read or write directly to main memory without any ...
Under the Amiga architecture, the direct memory access (DMA) controller is integrated into the Agnus (Alice on AGA models) chip. Both the CPU and other members of the chipset have to arbitrate for access to shared RAM via Agnus. This allows the custom chips to perform video, audio, or other DMA operations independently of the CPU.
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.
The Word DMA (WDMA) interface is a method for transferring data between a computer (through an Advanced Technology Attachment (ATA) controller) and an ATA device; it was the fastest method until Ultra Direct Memory Access (UDMA) was implemented.