What is DMA? Why does the DMA generally have priority over the CPU in the ease of accessing memory?

Subject Peripheral and Interfacing
NU Year Set: 2.(a) Marks: 4 Year: 2017

Direct memory access (DMA) is a method that allows an input/output (I/O) device to send or receive data directly to or from the main memory, bypassing the CPU to speed up memory operations. The process is managed by a chip known as a DMA controller (DMAC).

if you have a large block of data to be transferred over a system bus then DMA is called by the CPU.
the reason is if cpu monitor this transfer of data block then cpu will be not doing its useful job and reduces the performance of the system.
now is cpu give authority to DMA then DMA will interrupt cpu two time before actual transfer and at end when complete transfer has finished. This allows cpu to do its useful work while transfer is going on.
so DMA has to be given more priority then cpu is you don't want performance of the system to reduce.

Login to post your comment.