Different between virtual memory and physical memory?

Question

i wanted to know Different between virtual memory and physical memory and how much virtual memory we can have i mean virtual memory limits

Answer 1

Physical memory is much more expensive but much more faster than virtual memory.

Physical memory costs around $10 for 1 GB. The same 1 GB in virtual memory costs around $0.10 (ten cents) or less. Physical memory is very fast (as fast as the computer's processor/CPU is designed to run at) -- but virtual memory is much more slow (from 10000 to a million times slower).



So, you want to have more physical memory. Problem is, it costs much more. So you have to find a balance between the two. Most PCs and Macs today have about 1GB to 4GB of physical memory, and the rest in virtual memory. So the physical memory is mainly limited by how much you the buyer wants to pay for it.



The amount of virtual is limited by things like the operating system you have (e.g. Microsoft Windows 7 or Mac OS X), but also by the size of the hard-disk on your computer.



Most modern operating systems let you set aside up to 30% of your hard disk space, for use as virtual memory (this isn't a hard-rule, but they are designed internally for that - but their GUI might limit it to less).



This means when the CPU wants to, it can use the hard disk as a temporary place to keep it's data. The CPU will use this temporary (but slower) memory when its main physical memory (RAM) fills up. It's very complicated when the CPU does this, and what data it moves back-and-forth between physical and virtual memory. But it's controlled mainly by the operating system, and somewhat also by the programs you are running.



In most cases, you should setup your computer to have between 2% to 10% of your hard disk for virtual memory. In numbers, you want at least 3 GB to 15 GB of virtual memory to keep things fast. Any more would be wasteful (your CPU would almost never use it, but your hard disk would be shrunken because of this). And any less would not help keep your computer running fast.



Remember that the more virtual memory you give/setup, the smaller your hard disk will get (temporarily only - you can change this later).



BOTTOM LINE: Set your virtual memory to be somewhere between 6GB and 15GB (at least 3GB if your PC is old).



The actual amount depends on how much free space on (size of) your hard disk, and also how many programs/browsers/tabs you run at the same time. The more programs/browser-tabs you run, the bigger this should be. But if your hard disk is low on space (less than 10GB free), you should make the virtual memory a bit smaller by 1 or 2 GB (or more).



Hope this helps you keep your PC running smoothly & fast.

Answer 2

Physical memory is located on RAM chip(s) within your computer. Because they are physical, they limited to however much memory is located on the chips. Meaning if you have one 2 gb chip, then you are limited to 2 gb of information you can hold on that chip.



Often the memory will fill up, and the computer will need more memory than is physically available. This happens if you are running more than one program or opening large data files. So what Windows will do is to take part of what is in the physical memory and will move it to a file on the hard drive. This is called "virtual memory". Normally it will take something you are not using at the moment (such as pages that you are not currently displaying in a document) and move them out of physical memory and into this file.



However virtual memory is much much slower than physical memory. Access the hard drive is one of the slowest things a computer can do. You have probably seen the computer using virtual memory many times. For example, you will be reading a large document, and you go to scroll odwn to the next page, and everything stop for a second or two before that next page finally appears. That was your computer moving something out of physical memory to free up space, and then moving the pages you wanted back into physical memory so they can be displayed.



The more virtual memory you have available (meaning the larger you allow this swap file on your hard drive to be), the more programs you can run and the larger files you can open. But having all those programs open will also slow your computer because the use of virtual memory is much slower that physical memory.



You can make the virtual memory as large as you want. But unless your are trying to run 100 programs at the same time, it will probably never use all the virtual memory. It ony uses what it needs (thus the min and max settings - it can use whatever it needs between those two limits). A smarter idea is to just let Windows manage the swap file size, That way it is always going to be the size it needs to be at that moment. The "min and max" are a hold over from the days when hard drives were so tiny that giving up a few mb for virtual memory could run you out of hard drive space. Today, that is unlikely to happen. The virtual memory is normally about the size of a handful of mp3 songs. Hardly a drop in the bucket on today's hard drive, So just let Windows manage it for you.

Answer 3

Physical memory is, of course, the actual RAM installed in the machine. Virtual memory is a special file maintained by the system into which parts of active memory can be swapped into for later use thus freeing physical memory. The decision made by the system as to what can or cannot be swapped out is made by the programmers.



Virtual memory is limited by the size of the hard drive on which the swap file is installed but while there is no file size limit (except for whatever limits the file system itself puts on file size, like 4G for FAT32) there is a practical limit. As mentioned earlier not all elements residing in RAM can be swapped out and, more importantly, accessing swapped-out elements is very slow - hard drives are extremely slow compared to physical RAM access.

Answer 4

Physical Memory is just that... It is physical modules installed on your motherboard.



Virtual Memory (also referred to as the swap file or page file) is a Windows function that uses dedicated hard drive space to increase the ability of your physical memory. It is just basically a reserved spot on your hard drive to support memory related functions, that is all. Windows will manage its size based or your use.



Virtual memory is managed by Windows and really should never be tampered with.



If you are running into "Virtual Memory" errors, it is usually because your hard drive is too full to accommodate windows.



Virtual memory should not be considered "actual" memory and is not to be considered when determining system requirements. Virtual memory is VERY, VERY slow when compared to actual memory and does not replace physical memory functions interchangeably.

Answer 5

listen to Daniel!