Memory Access

Memory Access

Direct memory access
Anthony Ou
355
3/5/2013
Castle Phelps

Direct Memory Access
Should DMA access to main memory be given higher priority than processor access to main memory?
I believe the direct memory access should have the main priority access to main memory over the processor. Direct memory access is feature of computer hardware that allows devices to gain access to the main bus linking the processor to the system memory. Direct memory access moves data directly between the main memories or to another part of the system independently. Direct memory access can transfers memory a lot quicker than the processor itself. The processor must wait for the peripheral to respond in order to transfer any byte or words while the direct memory access directly has access and communicate with the peripheral to transfer the data.

  * What is the purpose and technique of DMA logic?

Direct memory access allows some of the hardware sub-systems to access system memory independently of its CPU. Without direct memory access, when the CPU is using input/output programs, it is typically occupied by the full duration of the read or write operation, and it cannot perform other work. With direct memory access, the CPU can initiates the transfer and does other operations while the transfer is in progress, and will be interrupted by the controller of the direct memory access when the operation is completed. Direct memory access is useful when the CPU could not keep up with the data transfer rate, and while the CPU needs to perform other useful work while waiting for a slow input and output data transfer. Many hardware systems use direct memory access such as disk drive controllers, graphics cards, and network cards. Computers that have direct memory access channels can transfer data from or to devices with much less CPU overloading than computers without a direct memory access channel. Just like the processing elements within a multi-core processor can transfer data from...

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