Search results
Results from the WOW.Com Content Network
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 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.
A certificate of analysis (COA) is a formal laboratory-prepared document that details the results of (and sometimes the specifications and analytical methods for) one or more laboratory analyses, signed—manually or electronically—by an authorized representative of the entity conducting the analyses.
The following example [9] reads a disk record identified by a recorded key. The track containing the record and the desired value of the key is known. The device control unit will search the track to find the requested record. In this example <> indicate that the channel program contains the storage address of the specified field.
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.
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.)
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.
B or b – prefix denoting a number in billions; BA – bottom assembly (of a riser) bbl – barrel bbl/MMscf – barrels per million standard cubic feet