The XBox One SoC and package
All of the major units are coherent with each other but the GPU has a direct non-coherent path that is basically AMD’s Garlic bus to main memory as well, a must for any modern CPU+GPU/APU/SoC. (Note: There isn’t a direct equivalent to Onion in the XBO SoC, that functionality is done with Microsoft’s IP) More interestingly is that while the 32MB of onboard memory is coherent with the CPU there is not a direct link between the two. How badly the added latency, if any, will hurt CPU code using this cache is not public but should make for some interesting arguments. In any case every block is coherent with every memory space and the system MMUs can make it all look seamless even if on-die and off-die memories are in different address spaces.
The system as a whole has a massive chunk of hardware devoted to AV tasks, enough to make background encoding, decoding, playback, scaling, and the rest about as seamless as possible to the gamer. AV should just work and gaming should just work regardless of what the other is doing, something the PS4 should do as well but in a very different way. Then again the majority of this functionality is available in a <$100 Android box so it isn’t a standout feature if you follow tech at all.
Then there are the GPUs themselves, the Achilles heel of the XBox One. While there is nothing wrong with them per se, they are a slightly older revision than used in the PS4 but the differences are small enough to be ignorable. What does matter is that the PS4 has about 50% more units at roughly the same clocks, 1152 at ~800MHz vs 768 at 853MHz, a massive difference. Couple this with the vastly more user-friendly 8GB GDDR5 memory design and you have a clean kill for Sony on performance.
Microsoft made a really impressive SoC that is a multimedia monster with a bit of gaming ability, technically speaking it is quite impressive that they pulled it off. Not to take anything away from the hardware designers but Microsoft management simply aimed wrong. Sony made a gaming machine, Microsoft did not. Sony made a clean design for coders, Microsoft did not. Microsoft made a complex technical masterpiece that is in a no-mans land between a far <$100 Android media center and the PS4. Sony just did right for gamers and won the battle.
