I think MS is using the Hyper V more for security questions than multitasking things.

They are creating two different environments into Xbone... one for Apps and other for Games... I'm pretty sure the SDK will be sold separately so you can have only the App SDK and not the game one.

It's like two different worlds inside the same hardware.

With the Xbox One, the Apps VM is constantly running, consuming its own piece of that 3GB of memory.  Switching between the Apps and Games VMs is just a matter of which one you're giving priority to the screen or what part of it.

In multitasking (PS4), you physically define priority in memory.  You're caching data active in physical memory to the HDD so that apps or games have priority.  This is the virtual memory discussed last week as a part of how memory works on the PS4.  In Sony's correction of Eurogamer, they referenced virtual memory.  If you do a search on virtual memory on FreeBSD, it's the same as cached memory (a HDD cache) found in Windows. 

Virtual memory can be used for saving active data for three reasons.  One, task switching, where the operating system needs access to memory.  Two, when an application must prioritize an operation, moving data active in physical memory to the cache (virtual memory) and freeing up the physical memory.  And three, when two different applications are running, and one has an operation that has priority over the any other operation the other application has.   

With the Xbox One there isn't caching within the 5GB and 3GB walls.  The Apps VM and HyperVisor have 3GB available to them.  So an app in memory stays in memory.  When the user switches from say playing Ryse to Skype full screen, the Games VM is suspended.  The Virtual Machine is simply frozen as are the contents of the memory.  Likewise when the user switches back to the game, the Apps VM may suspend depending on the context of the application.

There is no latency to unsuspend the VM.  You're not starting and stopping the VM.  It's like pausing a movie, then hitting the pause button to play it. 

Technically speaking, what Microsoft is doing is WAY cooler.  However, that said, to the consumer they will look virtually the same.

I think they're using it for both.

A VM has significant advantages with one small disadvantage.  The HyperVisor OS requires 512MB of memory, maybe less. 

You don't have to cache anything.  The VMs are both in memory.  You simply suspend the VM. 

I honestly believe the HyperVisor OS has the actual UI, with the apps running in the Apps VM and the games running in the Games VM.

Your not the only one:). People don't understand having somewhat fixed ram is mandatory. If developers create a game using 5 gigs, leaving 3 gigs for os it has to stay that way. I games created using 5 gigs won't run. They could later on however optimise or get rid of some features in app os to increase the fixed ram for game os. But stepping down available game ram would break almost every game.

Do not think of these VMs the same as the ones running on PC.  There is an article I have to find which talks about this a little more.  The Games VM is very thin.  Its hardware calls are pretty much no latency between it and the main VM.  The driver that MS has created that directly talks to the mettle is where all the work has been done and really is where you will see the most in optimizations.

This is kinda crazy. The advantage of using real memory instead of virtual memory for suspended applications offers such little improvement. Only reason it could be smart would be if Microsoft doesn't want to suspend apps but why would they do that? Best I can think of is playing a game with internet snapped to the side while a second game is in matchmaking, the youtube app is downloading a video, and you are talking on skype. Is this rare situation worth it?

This kinda goes back to xbone verse ps4 ram I guess. DDDR3 is cheap so they could get a lot of it. Back then the PS4 only had 2GB of ram so Microsoft logically thought the sky was the limit with multitasking. Why would they worry when they had so much extra? Then Sony jumped to 4 and again to 8. Now Microsoft's ram plans just seem wastefull.

I believe the Hyper-V tech expecially the one that runs everything is just a management type of system.  One of the big benefits is that the main Hyper V can dynamically turn on and off cores on the fly, management memory and resources.  This gives the X1 the ability to run in a bunch of power states for concerving power and resources and management between Games and Applications.  Its this separation that allows the games part to exist out side of the whole system and work independantly of whats going on within the X1.

Also one of the biggest things only on person has stated is that they Hyper-V tech allows MS to not have to worry about backwards compatibility.  This is one reason why we say different Development systems running X1 games.  If people remember E3 where Titans were running X1 development kits.  With this tech, the dependancy for true hardware becomes more abstract, probably ushering in that digital age where you can bring up different VMs to run diffeerent systems like the 360.

Another benefit of the hyper-V tech is the snap feature which regular MP will not be so easy to replicate.  With both running side by side you can have a companion app running to your main game which is something I am wondering if we will see on the X1 from developers.  One game that sounds like it will go this direction is Quantum Break.  You can have the TV episode running while you also have the game running and both can talk to each other and take ques thus producing something very unique.

I'm sorry but did you mean to quote someone else? I was talking about their decision to use physical memory instead of virtual for background apps. That has nothing to do with ANYTHING you said. lol

Not really.

First, I believe the two consoles will have similar footprints for games and non-gaming memory needs.

Second, while Microsoft could have done a lightweight OS, the path they took allows them to provide a highly secure environment and all the features they want to offer without compromise.