Assignment #4: Virtual memory manager
Dr. Romy Lu
Saturday, August 31, 2013
Most operating systems use a virtual memory manager (VMM) whose responsibility is to manage the relationship between the virtual organization of memory as seen by an application with the physical organization of memory from the operating system’s point of view. Virtual memory addresses must be mapped to physical address and vice versa.
Write a four to five (4-5) page paper in which you:
1. Differentiate between virtual memory and physical memory.
2. Evaluate the benefits gained by running applications when the operating system uses a virtual memory manager.
3. Analyze how virtual memory addresses get translated into physical addresses.
4. Analyze how a modern operating system translates 32-bit and 64-bit virtual addresses to physical addresses on the same machine.
5. Create a relationship diagram, using MS Visio or Dia, depicting the relationship between virtual addresses to physical addresses. Note: The graphically depicted solution is not included in the required page length.
Physical memory and virtual memory are two forms of memory used to store data in a computer. Physical memory refers to chips such as random access memory (RAM) and storage devices like hard disks or hard drives that are used to store data. Virtual memory is a memory space created by an operating system when the computer does not have enough physical memory to run a program. Virtual memory is created by combining the RAM with hard drive space. Virtual memory allows large programs to run faster when the RAM is not enough.
The physical RAM and hard drives in computers that are used to store data are the physical memory of a computer system (Martinez, 2013). In a computer’s operating system, application software and data currently used are stored in RAM, so they can be quickly accessed by the CPU. The RAM can be accessed faster than other storage devices like hard disk and CD-ROM. However, data exist in RAM only when the computer is switched on and working. When the power is off, the entire data in RAM disappears. The operating system and other data are loaded back to RAM from the hard drive when the computer is turned back on. The hard drive is what is termed, non-volatile memory, or memory that retains data even when it is powered off. It is composed of flat circular disks known as platters which save magnetic data. Data is written to and read from these platters.
Virtual memory is used when the computer lacks RAM space to run a program. Virtual memory is RAM space combined with the hard disk space. When the computer does not have enough RAM space to run a program, the data is transferred from RAM to a paging file by virtual memory, freeing up space in RAM (Net industries, 2013). A portion of hard drive is used to keep the page file. This process of transferring is done so quickly that the user does not feel any difference. Virtual memory can hold an entire block of data while the part which is getting executed remains on the RAM. So the virtual memory allows the operating system to run several programs simultaneously. Virtual memory increases the size of programs that could be executed and provides cost efficiency because hard disk space is cheaper than RAM memory space.
Because your computer has a limited amount of RAM, it is possible to run out of memory when too many programs or applications are running at one time (Gillard, 1997). This is where virtual memory manager comes into play. Virtual memory increases the available memory your computer has by enlarging the address space, or places in memory where data can be stored. It does this by using hard disk space for additional memory allocation. However, since the hard drive is much slower than the RAM, data stored in virtual memory must be mapped back and forth to real memory in order to be used. The…