2--x86 Processor

A program must be loaded into main memory before it

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: tes & Assignments visit: www.bsit.zxq.net 2.3 x86 Memory Management Downloaded From: www.bsit.zxq.net 47 same time to be much larger than the computer’s physical memory. The complete collection of pages mapped by the operating system is called virtual memory. Operating systems have utility programs named virtual memory managers. Paging is an important solution to a vexing problem faced by software and hardware designers. A program must be loaded into main memory before it can run, but memory is expensive. Users want to be able to load numerous programs into memory and switch among them at will. Disk storage, on the other hand, is cheap and plentiful. Paging provides the illusion that memory is almost unlimited in size. Disk access is much slower than main memory access, so the more a program relies on paging, the slower it runs. When a task is running, parts of it can be stored on disk if they are not currently in use. Parts of the task are paged (swapped) to disk. Other actively executing pages remain in memory. When the processor begins to execute code that has been paged out of memory it issues a page fault, causing the page or pages containing the required code or data to be loaded back into memory. To see how this works, find a computer with somewhat limited memory and run many large applications at the same time. You should notice a delay when switching from one program to another because the operating system must transfer paged portions of each program into memory from disk. A computer runs faster when more memory is installed because large application files and programs can be kept entirely in memory, reducing the amount of paging. 2.3.3 Section Review 1. What is the range of addressable memory in protected mode? 2. What is the range of addressable memory in real-address mode? 3. The two ways of describing an address in real-address mode are segment-offset and ______________. 4. In real-address mode, convert the following hexadecimal segment-offset address to a linear address: 0950:0100. 5. In real-address mode, convert the following...
View Full Document

This note was uploaded on 11/29/2013 for the course CSE 451 taught by Professor Hussein during the Winter '13 term at Fatih Üniversitesi.

Ask a homework question - tutors are online