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Virtual memory is a common part of most operating systems on desktop computers. It has become so common because it provides a big benefit for users at a very low cost.
Most computers today have something like 64 or 128 megabytes of RAM (random-access memory) available for use by the CPU (central processing unit). Often, that amount of RAM is not enough to run all of the programs that most users expect to run at once. For example, if you load the Windows operating system, an e-mail program, a Web browser and word processor into RAM simultaneously, 64 megabytes is not enough to hold it all. If there were no such thing as virtual memory, your computer would have to say, "Sorry, you cannot load any more applications. Please close an application to load a new one." With virtual memory, the computer can look for areas of RAM that have not been used recently and copy them onto the hard disk. This frees up space in RAM to load the new application. Because it does this automatically, you don't even know it is happening, and it makes your computer feel like is has unlimited RAM space even though it has only 32 megabytes installed. Because hard-disk space is so much cheaper than RAM chips, virtual memory also provides a nice economic benefit.
The area of the hard disk that stores the RAM image is called a page file. It holds pages of RAM on the hard disk, and the operating system moves data back and forth between the page file and RAM. (On a Windows machine, page files have a .SWP extension.)
Of course, the read/write speed of a hard drive is much slower than RAM, and the technology of a hard drive is not geared toward accessing small pieces of data at a time. If your system has to rely too heavily on virtual memory, you will notice a significant performance drop. The key is to have enough RAM to handle everything you tend to work on simultaneously. Then, the only time you "feel" the slowness of virtual memory is in the slight pause that occurs when you change tasks. When you have enough RAM for your needs, virtual memory works beautifully. When you don't, the operating system has to constantly swap information back and forth between RAM and the hard disk. This is called thrashing, and it can make your computer feel incredibly slow.
When your physical RAM fills up, it desperately needs another kind of temporary storage to be able to run your applications. Therefore, it creates a virtual memory right on your hard disk to satisfy that need. Data that is stored on the hard disk is stored in sectors, however, to the Memory Management Unit (MMU) of the Operating System, it is seen as though it is main memory. Before an application requests to run, the swap file is checked and if the data required by the application is found there, then it copies it over to memory first before executing it. Virtual memory is an excellent way of utilizing more memory than is physically available. Moving and swapping data between the physical memory and hard disk via the system bus is managed by the MMU as are the logical and physical addresses of each block of data.
Windows determines how much hard disk space to allocate to virtual memory. The good news is that you can make your system faster by manually altering your Virtual Memory settings. Follow these steps to get a noticeably faster PC:
Go to:
Start-> right click in MyComputer-> Properties-> Advanced-> Where Perfomance -> Settings->Advanced->Where Virtual Memory-> Settings->Initial Size = 800 Maximum Size = 4000 and done.
Most computers today have something like 64 or 128 megabytes of RAM (random-access memory) available for use by the CPU (central processing unit). Often, that amount of RAM is not enough to run all of the programs that most users expect to run at once. For example, if you load the Windows operating system, an e-mail program, a Web browser and word processor into RAM simultaneously, 64 megabytes is not enough to hold it all. If there were no such thing as virtual memory, your computer would have to say, "Sorry, you cannot load any more applications. Please close an application to load a new one." With virtual memory, the computer can look for areas of RAM that have not been used recently and copy them onto the hard disk. This frees up space in RAM to load the new application. Because it does this automatically, you don't even know it is happening, and it makes your computer feel like is has unlimited RAM space even though it has only 32 megabytes installed. Because hard-disk space is so much cheaper than RAM chips, virtual memory also provides a nice economic benefit.
The area of the hard disk that stores the RAM image is called a page file. It holds pages of RAM on the hard disk, and the operating system moves data back and forth between the page file and RAM. (On a Windows machine, page files have a .SWP extension.)
Of course, the read/write speed of a hard drive is much slower than RAM, and the technology of a hard drive is not geared toward accessing small pieces of data at a time. If your system has to rely too heavily on virtual memory, you will notice a significant performance drop. The key is to have enough RAM to handle everything you tend to work on simultaneously. Then, the only time you "feel" the slowness of virtual memory is in the slight pause that occurs when you change tasks. When you have enough RAM for your needs, virtual memory works beautifully. When you don't, the operating system has to constantly swap information back and forth between RAM and the hard disk. This is called thrashing, and it can make your computer feel incredibly slow.
When your physical RAM fills up, it desperately needs another kind of temporary storage to be able to run your applications. Therefore, it creates a virtual memory right on your hard disk to satisfy that need. Data that is stored on the hard disk is stored in sectors, however, to the Memory Management Unit (MMU) of the Operating System, it is seen as though it is main memory. Before an application requests to run, the swap file is checked and if the data required by the application is found there, then it copies it over to memory first before executing it. Virtual memory is an excellent way of utilizing more memory than is physically available. Moving and swapping data between the physical memory and hard disk via the system bus is managed by the MMU as are the logical and physical addresses of each block of data.
Windows determines how much hard disk space to allocate to virtual memory. The good news is that you can make your system faster by manually altering your Virtual Memory settings. Follow these steps to get a noticeably faster PC:
Go to:
Start-> right click in MyComputer-> Properties-> Advanced-> Where Perfomance -> Settings->Advanced->Where Virtual Memory-> Settings->Initial Size = 800 Maximum Size = 4000 and done.
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