UPDATE: I have added new info at the bottom of this post with more commentary from AMD (kind of).
You might have seen some reports in the last couple of days claiming that the upcoming Sony PlayStation 4 (PS4) will have a big advantage over the Xbox One thanks to its unique ability to support AMD's hUMA memory architecture. hUMA, heterogeneous unified memory architecture, is an exciting new memory technology that AMD has built into upcoming APUs.
Josh published a story on hUMA that sums it as so:
The idea behind hUMA is quite simple; the CPU and GPU share memory resources, they are able to use pointers to access data that has been processed by either one or the other, and the GPU can take page faults and not rely only on page locked memory. Memory in this case is bi-directionally coherent, so coherency issues with data in caches which are later written to main memory will not cause excessive waits for either the CPU or GPU to utilize data that has been changed in cache, but not yet written to main memory.
There's just one problem with these various reports (VR-Zone, ExtremeTech): they're incorrect. After sending some emails to our representatives at AMD I was told that "Kabini doesn't support hUMA" which is the APU that both the PS4 and Xbox One processors are based on. AMD further clarified with us:
Our spokesperson made inaccurate statements about our semi-custom APU architectures and does not speak for Microsoft, Sony or the AMD semi-custom business unit responsible for co-developing the next generation console APUs.
So while the PS4 will still be a faster system thanks to its higher SIMD processor (GPU core) count, there is no support for a true heterogeneous unified memory architecture in either upcoming console platform.
NOTE: I have had several people point out that it's possible Sony and Microsoft worked on their own custom memory architectures that will perform similar functionally to hUMA. That is entirely possible but means that official hUMA support isn't on the SoCs.
UPDATE: AMD contacted me again to make another comment. Essentially, they said that the correction statement to the original statement claiming hUMA was part PS4 was "inaccurrate" but that this correction does NOT mean the opposite claim is true. Even when pressed for a more specific and debate-ending comment, AMD wouldn't give us any more information.
So does the PS4 have support for some type of heterogeneous unified memory? Maybe. And the Xbox One? Maybe. At this point, I'd stop listening to anything AMD has to say on the subject as they are likely to recant it shortly thereafter. Many readers have emailed me with their thoughts and I personally feel that its more likely the original statement from AMD (that the PS4 will have the edge with a hUMA design) will turn out to be the truth in the long run…