Question

For the efficient memory management and to avoid errors modern systems uses secondary memory as a part of the main memory known as a virtual memory. When a computer system is running serval programs at the same time, the main memory often becomes exhausted. In such circumstances instead of closing some programs the operating system use the secondary memory as part of the main memory to store some data. In short virtual memory is an elegant interaction of hardware exceptions, hardware address translation and main memory as well as kernel software that empowers each process with a large, uniform and private address space. Virtual memory mainly provides efficient usage of the main memory, simplifies memory management as well as the protection of each address space from corruptions by other processes. In this regards, provide a detailed report on the following aspects of the virtual memory management. MEC_AMO_TEM_034_01 Page 2 of 10 Computer Architecture (COMP 0351) - Spring-20- CW (Assignment-2)-A-QP a) Explain how virtual memory management works. b) Critically examine the advantages and drawback of the virtual memory. (15 Marks) (15 Marks) Expectation: The literature is well supported with 4 or more in- text referencing and in text citations.

Answer 1

Task 3:

a) Virtual memory is a storage allocation scheme in which secondary memory act as an main memory or can be addressed as though it is a part of main memory.

Let's say that an OS needs 120 MB of memory in order to hold all the running programs.But there's currently only 50 MB of available physical memory stored on the RAM chips.The OS will then set up 120 MB of virtual memory and will use a program called virutal memory manager (VMM) to manage thOat 120 MB.

The VMM will create a file on the hard disk that is 70 MB (120-50) in size to account for the extra memory that's needed.The OS will now proceed to adress memory as if there were actually 120 MB of real memory stored in the RAM, even though there's only 50 MB.It is the responsibility of the VMM to deal with fact that there is actually 50 MB of real memory.

b) Advantages and drawbacks of virtual memory:

Drawbacks:

1) If the size of virtual memory is more than main memory , then more swapping to and from will occur in the hard disk which will result in slow performance of the OS.

2) Accessing the hard disk is far slower than using the RAM.

3)Using too many programs with insufficient amount of RAM results into thrashing. System performance will really slow down due to thrashing.

Advantages:

1) It allows you to run more application at once.

2)It helps you to fit many large programs into smaller sub programs.

3) It is used to implement multi programming enviroment.

4) There is no specific limit on the degree of the multiprogramming.

5) Common code or data may be shared between memory.

6) It also increase the effective use of CPU.

Task 4

a) A priority interrupt is a system which decides the priority of various devices , which generates the interrupt signal at the same time , will be serviced by the CPU.

The way of deciding the interrupt priority consists of serial connection of all the devices which generates an interrupt signals. The highest priority is placed at the top position followed by lower priority devices and device which has low priority among all is placed at the last in the chain.

In daisy chaining system all the devices are connected in serial form. Interrupt line request is common to all devices.If any device has interrupt signal in low level state than interrupt line goes to low level state and enables the interrupt input in the CPU.When there is no interrupt the interrupt line  stays in the high level state.The CPU respond to the interrupt by enabling the interrupt acknowledge line.