What is the need of dma in a computer? How is dma different than that of interrupt driven i/o technique? Assume that a new computer supports few bytes of input from multiple user's, which of the three i/o techniques is most suitable for this computer? Justify your answer?
Answers
Direct Memory Access is a strength given by some computer bus architectures that permits data to be sent directly from an attached device to the computer ROM.
Method that is used to transfer information between internal and external I/O devices is known as I/O interface.
Abstract level these look like a big pile of bytes organized into blocks of some size.
Abstract operations: read (blocks), write (blocks), seek (next block to read/write).
Character devices
These are stream of bytes with no particular structure embedded by the device.
Complex operations may provide very sophisticated functionality on top of what is provided by raw device.
Network devices
Somewhat similar to stream devices but separated by having built-in various high-level network protocols that add more structure
DMA is needed in a computer as it enables data to be transferred directly from an external device.
It is different from other interrupt driven I/O options as the microprocessor is not involved in the transfer, in turn, ensuring fast speed.
A Firewire port is the best option for a new computer that supports few bytes of multiuser input.
This is because, Firewire is a multiple bus port that enables high speed of input from multiple sources.