What IS Virtual Memory?

[Sir Goulum]

I'm kinda interested as to what it is exactly. Thanks! [img]smile.gif[/img]

[Lord Lothar]

I *think* it's space on your hard drive that is used by some programs as temperary memory.

[whacky]

Its kinda like an add-on for RAM except that it works on hard-disk space, atleast this is what my understanding of virtual memory is in terms of analogies [img]smile.gif[/img]

[Sir Goulum]

Hmm...I found a cool site...is this what Virtual Memory is/how it works, more or less?

Most computers today have something like 32 or 64 megabytes of RAM available for the CPU to use (see How RAM Works for details on RAM). Unfortunately, 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 operating system, an e-mail program, a Web browser and word processor into RAM simultaneously, 32 megabytes is not enough to hold it all. If there were no such thing as virtual memory, then once you filled up the available RAM your computer would have to say, "Sorry, you can not load any more applications. Please close another application to load a new one." With virtual memory, what the computer can do is look at RAM for areas that have not been used recently and copy them onto the hard disk. This frees up space in RAM to load the new application.

[Lord Lothar]

I think that's what whacky and I were trying to say. [img]smile.gif[/img]

[Sir Goulum]

Originally posted by Lord Lothar: I think that's what whacky and I were trying to say. [img]smile.gif[/img]

AH! So you were! [img]tongue.gif[/img]

[whacky]

Originally posted by Sir Goulum: quote: Originally posted by Lord Lothar: I think that's what whacky and I were trying to say. [img]smile.gif[/img]

AH! So you were! [img]tongue.gif[/img] [/QUOTE]An elder orb eh ? Your avatar sure looks funny to me [img]tongue.gif[/img] [img]tongue.gif[/img]

[WillowIX]

The perfect description of Virtual memorey is: what you always run out of [img]tongue.gif[/img]

[Animal]

Space set aside on your hard drive by the operating system to cache files and programs to when you run out of physical RAM. It's not very effecient, but if you've got several programs open, the OS will send the ones your not using to virtual memory so the program your working with has full access to your physical RAM. Clear as mud?

[Sir Krustin]

Virtual memory is memory that doesn't exist, but is nevertheless mapped out for use by client applications. Intel '386 and later CPUs have 4GB of addressable address space and ALL of that is available for use, regardless of whether or not the memory chips are physically present.

The OS gets around the limitations of physical memory by "swapping" out pages of memory to harddisk temporarily that are not currently needed. When the data stored on those pages of memory is again needed, the OS recalls them from the HD and puts them back into physical memory so they can be used. This may mean that _other_ pages of memory may be in turn swapped to the disk for temporary storage.

When the calls for memory become so frequent that the HD is contually busy (called "thrashing"), you have reached the practical limit of virtual memory, usually much less than the theoretical limits.

This is why installing more physical memory can dramatically improve system performance in a multitasking system.