In one paragraph he says he has four gigabytes of memory, and after switching to LInux, he says he has eight.
It seems he's misunderstanding inactive memory, which can be either filesystem caching (since it's already backed on disk, can be freed with no penalty) or allocated memory by the processes but not recently used (which would count as used under Linux, and when running out of free mem, would be paged to disk on both Linux and Mac OS X).
It seems he's misunderstanding inactive memory, which can be either filesystem caching (since it's already backed on disk, can be freed with no penalty) or allocated memory by the processes but not recently used (which would count as used under Linux, and when running out of free mem, would be paged to disk on both Linux and Mac OS X).