Understanding the computer -What is Direct Memory Access?

Direct Memory Access is shortly known as DMA. Usually, all the data transferred between different devices of computer have to move through CPU. DMA is a technique supported by modern computers through which data can be sent between different peripheral devices without intervention of CPU. Since the data is not intervened by CPU in middle, the overall time taken for the transfer of data from one source to there is less compared to ordinary computers. The new hardware supports Ultra DMA though which data can be sent more effectively than the present DMA technique.

Usually, small portion of the RAM is divided for both DMA transfer as well as normal transfer of the data. DMA is also used for multi-tasking. Different types of DMA operations are single transfer, block transfer, burst-block transfer, repeated single transfer, repeated block transfer, repeated burst-block transfer. The DMA is works in low power mode as it uses the one and only available bus for transferring the data which is always busy with CPU. DMA is used in multi-core processors especially for the transfer of data between various processors at a high speed. DMA may cause cache coherency problems, it can’t differentiate between the external memory and cache but this can be solved.