Una delle feature più chiacchierate e meno comprese di Windows, addirittura sin dai tempi di Vista, è quella di SuperFetch, una cache predittiva abbastanza evoluta. Usata anche a sproposito per spalare cacca su Windows.
In Apple hanno pensato di fare una cosa simile inventando la inactive memory:
This information in memory is not actively being used, but was recently used.
For example, if you've been using Mail and then quit it, the RAM that Mail was using is marked as Inactive memory. This Inactive memory is available for use by another application, just like Free memory. However, if you open Mail before its Inactive memory is used by a different application, Mail will open quicker because its Inactive memory is converted to Active memory, instead of loading Mail from the slower hard disk.
Bella pentola, ma come al solito si sono scordati il coperchio:
that this memory may be freed at any moment. However in practice, it just keeps on accumulating until you run out of free memory. In this case a sane option for the OS would be freeing the inactive memory. Instead the OS X decides toswap the inactive memory on the disk. So when running out of free memory and having a 1,5 gigabytes of inactive memory left, your OS starts paging the unused inactive memory to disk instead of freeing it for applications to use. Not only this causes your computer to slow down, it also is counter-intuitive in the terms of the original idea of inactive memory: when it's on disk, it definitely is not made active quickly.