1.)Why would DMA be useless if the computer did not have interrupt capability? 2
ID: 3596023 • Letter: 1
Question
1.)Why would DMA be useless if the computer did not have interrupt capability?
2.) What is an interrupt vector?
3.)To use a computer for multimedia (moving video and sound), it is important to
maximize the efficiency of the I/O. Assume that the blocks of a movie are stored consecutively on a CD-ROM. Describe the steps used to retrieve the blocks for
use by the movie display software. Discuss ways in which you could optimize the
performance of the I/O transfer?
4.)What is the difference between polling and polled interrupt processing?
5.)Describe the steps that occur when a system receives multiple interrupts
i need answers for these questions maximum a 4-5 lines
Explanation / Answer
1)Answer:
DMA be useless if the computer did not have interrupt capability because Without interrupts, the CPU would never be notified of the DMA's completed actions.
Explanation:
DMA, direct memory access, is a technique which uses an independent sub-component of your hardware to access your computer's RAM (usually, although it could be other types of memory) independent of the CPU (saving processing time).
Basically, you talk to the DMA controller and tell it something like "okay, go to this address, and grab me 10000 bytes of data, and put it at this address", then the DMA controller tries to perform the operation.
But what happens when it's done?
How does the DMA controller tell the CPU that it finished the operation? You guessed it!
It "interrupts" the CPU from what it's doing; the CPU can set up the next DMA request, and then go back to what it was doing, until the next interrupt arrives.
So, without interrupts, the CPU would never get notified of the DMA's completed actions.
Obviously, interrupts can be (and are) used in many other contexts. For example, pressing a key on a keyboard could generate an interrupt. How the CPU identifies one interrupt from another is getting too heavy into the details, but you are free to do some further reading. ;
2)Answer:
interrupt vector:
An interrupt vector is the memory location of aninterrupt handler, which prioritizes interrupts and saves them in a queue if more than one interrupt is waiting to be handled.
4)Answer:
difference between polling and polled interrupt processing:
The difference in the simplest terms will be polling is “I’ll ask you” and interrupt is “You tell me.”Examples that I can relate to will be cooking, whencooking there are several tasks going on at the same time.If I plan on fixingchicken and mashed potatoes I will ask what to do first.If I were to use thepolling method, I will fix the potatoes first and they will need to be completedbefore I can move on to fixing the chicken.However, if using the interruptmethod I can prepare the chicken and place my thermometer in the chickenwhich will alert me to the fact I need to stop with the potatoes then check thechicken.Then a similar alert or interrupt can be placed with the potatoes so I cankeep going back and forth between the two dishes and in the end both dishes willbe completed at the same time.With computers, the efficiency will be degraded if the program had tocomplete one task before checking to see if other tasks need to be completed.The interrupts greatly improves this efficiency because it can let the computerknow it is time to perform another task.
5)Answer:
steps that occur when a system receives multiple interrupts:
If we encounter with multiple interrupts, first interrupt makes a suspension of the program executing at the time, memory of program's critical parameters and transfer of control to the program which are handles the determined interrupt. After first interrupt, the second interrupt occurs. Second interrupt's priority is compared to that of the original interrupt. When its priority is bigger, it gets precedence and the original interrupt program is itself suspended. In the contrary, processing of the real (original) interrupt keeps going and the new interrupt is caught on till the original interrupt program is complete. If the higher priority interrupt process is completed, the lower interrupt is processed. When any interrupts do not occur and when any interrupt's result do not occur in the suspension of all CPU processing, control eventually turn back to original program which then resumes processing. Generally, multiple interrupts cause in a queue of interrupt handler programs. These programs are executed by priorities associated with each interrupt.
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