Console Makers' OS (CMOS!1111)
Over time the memory footprint of the OS goes down, meaning more memory can be used for gaming and other things.
I wouldn't hold my breath on that. Assuming the 3 GB reservation for the OS is true that does NOT mean the OS itself is using 3 GB of memory. Basically it just means that 3 GB is offlimits to games. That 3 GB will presumably be used for everything else that isn't a game.
Hence it doesn't matter if the OS uses 256 MB or 512 MB or 384 MB at launch or whatever else number it ends up being. If that footprint is reduced in the future there will still be a 3 GB reserved space. In a case like that, it'll just mean more memory available for applications other than games.
Think of it another way. 3 GB are reserved for the OS and applications. 5 GB is reserved for games.
So the OS and applications cannot steal memory from games and the games can't steal memory from the OS or applications.
The practical benefits is that background tasks and applications in theory never have to be unloaded when playing a game. Video transcoding, video messaging, skype, video recording, whatever, doesn't have to be evicted from memory and if required doesn't have to be put on hold. Likewise games don't have to be evicted from memory if you wish to check e-mail, watch a youtube video on how to get X secret in game, look up information on the internet in the browser or whatever.
If rumors are true that 2 or 3 cores are reserved for the OS, that definitely guarantee's that you can have multitasking always on background applications (the above mentioned video conferencing, video recording, video transcoding, for example) without impacting gameplay in the the slightest. The games will always have exclusive access to 5 or 6 cores. The OS and applications will always have exclusive access to 2 or 3 cores. Or however things end up being split.
In fact, with things reserved in such a manner it already gives an advantage over say a PC in that there are set resource boundaries over which there won't be contention over resources. A game for example would never be in a position where it would share a CPU core with applications or drivers as an example.
For PS4, I'm going to guess it'll have the more traditional model of having to unload a game to fully utilize all of the non-game home media center type tasks. Assuming it wants to provide a similar living room experience to the next Xbox. Basically the always on services and applications will be far more limited. With more feature rich applications requiring a game not be running in order to use them.
Regards,
SB