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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.
In computing, bus mastering is a feature supported by many bus architectures that enables a device connected to the bus to initiate direct memory access (DMA) transactions. It is also referred to as first-party DMA , in contrast with third-party DMA where a system DMA controller actually does the transfer.
It then instructs the DMA hardware to begin the transfer. When the transfer is complete, the device interrupts the CPU. Scatter-gather or vectored I/O DMA allows the transfer of data to and from multiple memory areas in a single DMA transaction. It is equivalent to the chaining together of multiple simple DMA requests.
Some examples of "complex" instructions include: transferring multiple registers to or from memory (especially the stack) at once; moving large blocks of memory (e.g. string copy or DMA transfer) complicated integer and floating-point arithmetic (e.g. square root, or transcendental functions such as logarithm, sine, cosine, etc.)
For example RDMA over Converged Ethernet (RoCE) now is able to run over either lossy or lossless infrastructure. In addition iWARP enables an Ethernet RDMA implementation at the physical layer using TCP / IP as the transport, combining the performance and latency advantages of RDMA with a low-cost, standards-based solution. [ 2 ]
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.
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.
Fault Management – Report errors from the device, query about status of device; All of the above functions are supported by the OMA DM specification, and a device may optionally implement all or a subset of these features. Since OMA DM specification is aimed at mobile devices, it is designed with sensitivity to the following: