I recently switched to a Mac, and have a laptop with 4GB of ram. When I look in the prosess explorer, I can see that almost all the memory is used, there is only a few hundred MB left. But almost 2GB is said to be "Inactive".

What does this means? My best guess is that this memory is free to be used by any applications, but is "reclaimable" by the original applications, eg. that the content is kept in place.

Anyone know the details?

2 Answers 2


Usually all available memory is put to use by the operating system as disk cache. What is already in memory doesn't need to be loaded from disk. When a program requests memory then necessarily the cache gets smaller.

The Windows Task Manager doesn't show this part of memory as "used" in contrast to the one in OS X. But they both do essentially the same thing there.


I think you'll find that Windows Vista and Windows 7 behave similarly to Mac OS X. Rather than having memory sit out there wasted, they use it as a cache, but make it available to apps when needed.


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