Skip to main content

Direct memory access in operating system-computer world

                             Direct memory access 

Direct memory access : DMA stands for  direct memory access and it is another mechanism where input output device is given full transfer block of data to from memory without going through the CPU. In other word we can say that it is a method of transferring data from the computers RAM to another part of computer. The DMA controller operate the memory bus directly without the help of main CPU so DMA controller improves the system performance.

Whenever a device uses DMA , it has to specify a DMA channel . Ultra DMA hard drive uses DMA to transfer at high speed. Whereas earlier hard drives were the first to transfer data from CPU which took more time. 

In older computers , the four DMA channel were 0, 1, 2 and 3 were used , when the 16 bit ISA bus was introduced, the channels 5, 6 and 7 were also added to it.

DMA transfer modes

1. Burst mode : Burst mode is the fastest DMA mode in which two or more bytes can be continuously transferred.

2. Cycle steal mode : Cycle steal mode is slower than burst mode. In this mode only one byte is transferred at a time.

3. Transparent mode : This is the slowest data transfer mode in which the processor executes some status that makes it different from the system bus.

Comments

Post a Comment

Popular posts from this blog

Deadlock in operating system-computer world

  Deadlock in operating system-computer world Deadlock :  In a multi-programming environment, many process may complete for a minute number of resources. A process make a request for a resource and if the resource is not available at that time, the process enter In a waiting state. A waiting state process is never again-able to change state because the resource it has requested is held by other waiting process. This situation is called deadlock. So we can say that a process is said to be deadlock when it is waiting for an event or resources which will never occurs.   so we can say that in this situation none of the process gets executed  since the resource it needs, is held by some other process which is also waits for some other resource to be released.  Let's assume that there are three process P1, P2, p3 and three different resources R1, R2 and R3. R1 is assigned to p1, R2 is assigned to P2 and R3 is assigned to P3.   After somet...
9 comments
Read more

What is sound card, video card, TV tuner card and network adapter card-computer world

 What is sound card, video card, TV tuner card and network adapter card Sound card :  Sound card is also known as audio card, sound sound board or audio output device. Sound card is a expansion card that provide the input and output of audio signals to and from a computer under control of computer programs. It is an expansion card for producing sound on computer that can be heard by speakers and headphones.  Uses of sound card :  Sound card is used for for providing the audio component  for multimedia application such as video auditing , audio auditing .It is also used in the field of education.  Video card :  It is an expansion card that connect to a computer motherboard. Video card is also known as video adapter or video controller. It is used to create a picture on display. TV tuner card : A  TV tuner card is like a television tuner that allow single to be received by a computer. TV tuner c...
2 comments
Read more

What is computer and its characteristics-computer world

  What is computer and its characteristics  Computer  :  Computer is an electronic data processing device, which accept and store data input, process the data and generates the output in a required format. computer is made up of integrated  parts (input, control, ALU, storage and output unit) All the part work together to process data so, we can say that a computer is a programmable electronic device accept row data as input and process it with  set of instruction to produce the result as output. Meaning of computer The word "computer" comes from the word "compute" which means to "calculate". The word computer is derived from the Latin word compute which means to calculate. Characteristics of computer Automatic : It is a automatic machine work by itself without human instruction. Speed :  A computer is a very fast devices. It can perform in a few second, the amount of work that a human being can do in an entire year.  Accuracy : In addition t...
1 comment
Read more