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CS609 System Programming Assignment No 3 Solution & Discussion Due Date: 26/Jun/2013

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What is DAP? it is not in hanouts

DAP is Disk Address Packet 

please share simple idea...

koe to solution idea upload kar day...bna khud lain ga....

aoa

koi 2nd question ka answer upload kr dy plss.

time boht short hy plsss anyone help

Yes we can use DMA in protected mode because DMA is a technique which  allows a peripheral to read from and/or write to memory without

 intervention by the CPU. It is a simple form of bus mastering where

 the I/O device is set up by the CPU to transfer one or more contiguous

 blocks of memory.

 After the transfer is complete, the I/O device gives control back to the CPU.

 The following DMA transfer combinations are possible:

 •        Memory to memory

 •        Memory to peripheral

 •        Peripheral to memory

 •        Peripheral to peripheral

 The DMA approach is to "turn off" the CPU and let a peripheral device

 communicate directly with the memory (or another peripheral). In

 protected mode CPU allows system software to use features such as

 virtual memory, paging and safe multi-tasking designed to increase an

 operating system's control over application software. Each program can

 be allocated a certain section of memory. Other programs cannot use

 this memory, so each program is protected from interference from other

 programs. Primary advantage is that CPU never stops executing its

 programs and DMA transfer is free in terms of time.

 Disadvantage is that the hardware needed to determine when the CPU is

 not using the system buses can be quite complex and relatively

 expensive

see http://www.zeepedia.com/read.php?direct_memory_access_dma_advance_c...

http://en.wikipedia.org/wiki/Protected_mode

ye CS501 lecture #31

Question 1:                                                                                                                               

 

Can we use DMA in protected mode or virtual mode of memory? Explain your answer with a solid reason.

Solution:

 

The process for performing DMA transfers in the protected mode Windows environment should be similiar to the process for performing DMA transfers in the real mode MS-DOS environment. In both environments, you must initialize the DMA controller with the starting base address, page address, transfer count, and mode. In both environments, you would usually install a hardware interrupt handler to handle terminal count interrupts when a DMA transfer is complete.

 

 

Question 2:                                                                                                                               

 

Compare all accessing mechanisms of a magnetic disk with limitations and uses, and which mechanism will be used for accessing of 1 Terabyte disk?

 

Solution:

 

Magnetic storage media can be classified as either sequential access memory or random access memory although in some cases the distinction is not perfectly clear. The access time can be defined as the average time needed to gain access to stored records. In the case of magnetic wire, the read/write head only covers a very small part of the recording surface at any given time. Accessing different parts of the wire involves winding the wire forward or backward until the point of interest is found. The time to access this point depends on how far away it is from the starting point. The case of ferrite-core memory is the opposite. Every core location is immediately accessible at any given time.
Hard disks and modern linear serpentine tape drives do not precisely fit into either category. Both have many parallel tracks across the width of the media and the read/write heads take time to switch between tracks and to scan within tracks. Different spots on the storage media take different amounts of time to access. For a hard disk this time is typically less than 10 ms, but tapes might take as much as 100 s. The optical disc revolution started with CDs and then moved on to DVDs, and we're in the midst of the next-gen battle between HD DVD and Blu-ray. Since the birth of the CD 25 years ago, we've gone from 600MB to a whopping 50GB of storage capacity on these little, convenient and versatile discs. The company claims that they can store up to 1TB (1,000GB) on an optical disc with the same dimensions—only slightly thicker—than a regular DVD and will be able to store 5TB once the jump to blue lasers is made. The 1TB disc is divided into 200 different layers, each comprising 5GB of storage space. Unlike standard multilayer DVDs, the layers aren't physically stacked and stuck together.



tariq bhai dosrey question ka yeh answer theak hai kya?

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