pleases answer 9.1, 10.3, 10.10 Thank you!! 9.1 Why would DMA be useless if the
ID: 3738088 • Letter: P
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pleases answer 9.1, 10.3, 10.10
Thank you!!
9.1 Why would DMA be useless if the computer did not have interrupt capability? 10.3 A multiplattered hard disk is divided into 1100 sectors and 40,000 cylinders. There are six platter surfaces. Each block holds 512 bytes. The disk is rotating at a rate of 4800 rpm. The disk has an average seek time of 12 msec a. What is the total capacity of this disk? b. What is the disk transfer rate in bytes per second? c. What are the minimum and maximum latency times for this disk? What is the average latency time for this disk? 10.10. A high-quality photographic image requires 3 bytes per pixel to produce sixteen million shades of color a. How large a video memory is required to store a 640 x 480 image during display? A 1600 x 900 image? A 1440 x 1080 image? A 2560 x 1440 image? b. How many 1920 x 1080 non-compressed color images will fit on a 4.7 GB DVD- ROM?Explanation / 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.
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