Xbox One locks away around ten per cent of its GPU power from developers… for now.
Microsoft technician Andrew Goossen says that the resources are dedicated to system processing such as Kinect and the system's multitasking snap mode. But in the future these resources will be opened up to developers.
"The current reservation provides strong isolation between the title and the system and simplifies game development,” he told Digital Foundry. Strong isolation means that the system workloads, which are variable, won't perturb the performance of the game rendering.
In the future, we plan to open up more options to developers to access this GPU reservation time while maintaining full system functionality."
Goossen also explained why developers aren't required to have their game output at a native 1080p.
"We've chosen to let title developers make the trade-off of resolution vs per-pixel quality in whatever way is most appropriate to their game content,” he explained. A lower resolution generally means that there can be more quality per pixel.
With a high quality scaler and anti-aliasing and render resolutions such as 720p or '900p', some games look better with more GPU processing going to each pixel than to the number of pixels; others look better at 1080p with less GPU processing per pixel.
"We built Xbox One with a higher quality scaler than on Xbox 360, and added an additional display plane, to provide more freedom to developers in this area. This matter of choice was a lesson we learned from Xbox 360 where at launch we had a Technical Certification Requirement mandate that all titles had to be 720p or better with at least 2x anti-aliasing – and we later ended up eliminating that TCR as we found it was ultimately better to allow developers to make the resolution decision themselves.
Game developers are naturally incented to make the highest quality visuals possible and so will choose the most appropriate trade-off between quality of each pixel vs. number of pixels for their games."