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Physical memory(MB) for Windows 7

Total 4021
Cached 1113
Available 768
Free 174
Memory used 3.25GB

At this point, windows7 asks me to close some programs because "system memory is low". From my understanding reading articles, I still have 768 MB free memory, why does windows7 complain?

Also what does Cached memory refer to? Is this part of memory that Windows7 reserved for itself meaning it's free to use by Windows7 (and means I have about 768 + 1113 MB of free mem?)?

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Understanding the "3GB not 4GB" RAM problem...asisupport.com/ts_4GB_memory_info.htm –  Moab Sep 18 '10 at 0:14
    
All about Windows 7 memory management Part 1..blogs.msdn.com/b/tims/archive/2010/10/28/… –  Moab Apr 3 '11 at 21:42
    
Part 2...blogs.msdn.com/b/tims/archive/2010/10/29/… –  Moab Apr 3 '11 at 21:43

2 Answers 2

If you're running Windows 7 in 32 bit mode you will NOT have a full 4 GB available to begin with.

The cached memory is typically used by the disk system to speed things up by pre-reading stuff or keeping old disk buffers available in case they need to be re-used. Win7 will typically use this heavily - which is usually a good thing. It's not "free" memory in any sense of the word.

If you're running a VM then you have an entirely different problem. Try to make sure you're not over-committing RAM to the VM. Look at your XP task manager and if your RAM usage while running your normal programs is a low percentage (25% or lower) you might think about reducing the RAM allocated to the XP VM.

As harrymc said, don't disable the page file. If its heavily used - you're right, that IS a bad thing, but it will keep your system running instead of crashing.

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Free memory is memory which has not been allocated for any purpose yet. Available memory is memory which was recently used by an application, and is likely to be used again, but it can be given up temporarily if needed (think, you minimized an application. Part of that application's memory can be reused until you restore the application and continue using it. This is what causes the long delay when restoring a minimized application on RAM-starved systems). Cached memory is memory which the system is using as a system cache for files which have been recently fetched from the harddrive.

As a general rule, windows will move stuff to the page file as RAM fills up, with increasingly severe performance degredation until the page file fills up, which is when it usually displays the low system memory at about 100-200mb of free memory left (or for me, anyways).

You might take a look at your "commit size" with the tool Process Explorer by Sysinternals (More or less Task Manager on steroids). This will tell you how much of the total available virtual memory is in active use. If the peak is close to the limit, then you might consider increasing the size of your pagefile or installing more memory.

Are you running a 64-bit copy of windows or a 32-bit copy of windows with a high-end graphics cards (ones with 512mb or more of video memory)? Because of the way addressing works, 32-bit windows can only "see" 4GB of memory, and this includes video memory. So if you have a graphics card with 512mb of memory, windows only really has 3.5gb instead of your total 4021mb to play with. If this is the case, you might consider switching to a 64-bit OS.

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