Well-placed development sources have told Digital Foundry that the ESRAM embedded memory within the Xbox One processor is considerably more capable than Microsoft envisaged during pre-production of the console,
with data throughput levels up to 88 per cent higher in the final hardware.

Bandwidth is at a premium in the Xbox One owing to the slower DDR3 memory employed in the console, which does not compare favourably to the 8GB unified pool of GDDR5 in the PlayStation 4.
The 32MB of "embedded static RAM" within the Xbox One processor aims to make up the difference, and was previously thought to sustain a peak theoretical throughput of 102GB/s -
useful, but still some way behind the 176GB/s found in PlayStation 4's RAM set-up.
Now that close-to-final silicon is available, Microsoft has revised its own figures upwards significantly, telling developers that 192GB/s is now theoretically possible.

So how could Microsoft's own internal tech teams have underestimated the capabilities of its own hardware by such a wide margin?
Well, according to sources who have been briefed by Microsoft, the original bandwidth claim derives from a pretty basic calculation -
128 bytes per block multiplied by the GPU speed of 800MHz offers up the previous max throughput of 102.4GB/s. It's believed that this calculation remains true for separate read/write operations from and to the ESRAM.
However, with near-final production silicon, Microsoft techs have found that the hardware is capable of reading and writing simultaneously.
Apparently, there are spare processing cycle "holes" that can be utilised for additional operations.
Theoretical peak performance is one thing, but in real-life scenarios it's believed that 133GB/s throughput has been achieved with alpha transparency blending operations (FP16 x4).

The news doesn't quite square with previous rumours suggesting that fabrication issues with the ESRAM component of the Xbox One processor had actually resulted in a downclock for the GPU, reducing its overall capabilities and widening the gulf between graphical components of the Xbox One and the PlayStation 4. While none of our sources are privy to any production woes Microsoft may or may not be experiencing with its processor, they are making actual Xbox One titles and have not been informed of any hit to performance brought on by production challenges. To the best of their knowledge, 800MHz remains the clock speed of the graphics component of the processor, and the main CPU is operating at the target 1.6GHz. In both respects, this represents parity with the PlayStation 4.

In terms of what this all means with regards multi-platform titles launching on both next-gen consoles,
our information suggests that developers may be playing things rather conservatively for launch titles while dev tools are still being worked on.
This is apparently more of an issue with Xbox One, where Microsoft developers are still in the process of bringing home very significant increases in performance from one release of the XDK development environment to the next.
Our principal source suggests that performance targets are being set by game-makers and that the drivers should catch up with those targets sooner rather than later.
Bearing in mind the stuttering performance we saw from some Xbox One titles at E3 such as Crytek's Ryse (amongst others), this is clearly good news.

As the performance levels of both next-gen consoles are something of a moving target at the moment, differences in multi-platform games may not become evident until developers are working with more mature tools and libraries.
At that point it's possible that we may see ambitious titles operating at a lower resolution on Xbox One compared to the PlayStation 4.

Via Gaf