How Xbox One's operating systems work - why setting aside RAM for apps is good for devs and gamers

Microsoft talks us through finding the balance between features and games

Xbox One offers a total of eight gigabytes of RAM, a stupendous leap over its predecessor's 512 MB - but around three gigabytes of this is set aside for entertainment apps, system-wide Kinect features and communication tools like Skype, which run in parallel to games. Naturally, this has provoked a certain amount of upset among those who'd rather each and every byte of memory was set aside for the sole, exclusive purpose of, say, rendering folds in Batman's cape.

According to Xbox's director of development Boyd Multerer, however, that kind of all-or-nothing thinking simply isn't reflective of the myriad functionality players now expect of their consoles. Xbox One's operating system setup, he argued, is an attempt to reconcile this hunger for supposedly "peripheral" features with the stability developers require of console hardware. Speaking to us shortly before the console's reveal, Multerer explained Microsoft's thinking in greater depth: how it built Xbox One to serve as both a fixed games platform for developers to target, and something more flexible for rapidly-changing apps of the moment - rather than trying to cram the latter into the former, as with Xbox 360's unloved Twitter app.


A quick recap, for those who missed our Xbox One guide in May. The new console runs three "virtual machines", two on top of a third. The heftiest is a partition that's exclusively for games, which sits alongside a lesser Windows-derived partition that's exclusively for apps and system-wide features. Beneath these is a hypervisor that manages the distribution of hardware resources between the two. Running these virtual machines in parallel contrasts to older consoles like the PS2, where the hardware "literally reboots into the game which has its own operating system, which then takes over the entire machine".

Xbox One's gaming partition gets the "majority of the resources of the box", according to Multerer, and runs a "very thin" (that's to say, non-memory intensive) operating system - so "thin", in fact that games "pretty much sit right on top of the hardware", granting all but unfettered access to its capabilities. It gets the lion's share of the machine's processing power when games are playing, too - around 90% - though the amount of memory available is fixed.

Meet the new crowd
Xbox 360 already divides its memory allowance, in order to run the dashboard Guide on top of games, but there's now much more pressure to save RAM for so-called "broader entertainment" and networking features. "The next generation gamer is not necessarily the gamer I was when I was getting into gaming," Multerer told us. "There are real differences, real changes that have happened since we began the last generation."

For one thing, most living rooms are now awash with portable entertainment hardware, from laptops to smartphones, and consumers are accustomed to running two or more of them at once - checking Twitter while sitting through a Call of Duty cutscene, for instance. Moreover, these devices are conduits to a vast, chaotic, relentlessly distracting universe of software and content.


"There has been an explosion of devices," Multerer went on. "There are phones, there are tablets, the whole way that people interact and that they live with devices has fundamentally changed. I walk around with a phone all time, everybody I know walks around with phones. The expectation of the next gen gamer is that these things are just there. It's a rapidly changing ecosystem of applications that sit on a rapidly changing ecosystem of devices - fundamentally different to the consoles of the past."

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