Digital foundry, xbox one is officially 33% weaker than PS4
Spec Analysis: Xbox One
Is PlayStation 4 really more powerful?
As a core gamer, it's difficult not to be frustrated by the manner of yesterday's Xbox reveal. Microsoft set out to champion its innovative platform, its vision for multimedia and a renewed focus on making Kinect relevant again as a convincing alternative to the traditional remote. But we wanted to know about the new generation of gaming and the approach in revealing Xbox One titles via trailers with no single identifiable example of actual live gameplay was an enormous error in judgement. The problem is that next-gen trailers look no different to current-gen trailers - so there was no groundbreaking innovation, no authenticity and therefore no buzz. Even the promising Call of Duty: Ghosts reveal - perhaps the closest thing we had to actual gameplay - was in-engine footage apparently running on Xbox One hardware. Yet there were no assurances that this was actually real-time, or that this would be the actual quality of the game we will be playing in November.
There was a similar level of inscrutability about the actual specs of the Xbox One hardware too. In the presentation itself, Microsoft talked in broad strokes about the internals of the box - eight CPU cores, 8GB of (non-descript) RAM, multi-channel 802.11n WiFi, and a Blu-ray drive. But the only new information we had that hadn't previously leaked was the inclusion of a 500GB hard drive and a five billion transistor count for the main processor. Gaming specs like the CPU clock-speed, the type of RAM, the make-up of the graphics core - all the most controversial elements of the leaked information, in other words - were ignored. The cynical may suggest that highlighting this would do Xbox One no favours in comparison to the PlayStation 4, while the Microsoft faithful could perhaps hold out hope that the more disappointing elements of the previous leaks were outright wrong.
A follow-up architecture panel hosted by Microsoft's Larry Hyrb soon put paid to the latter, more optimistic appraisal of the situation. Very early on it was established that ESRAM is indeed incorporated into the Xbox One design - essentially a large, very fast cache of embedded memory attached to the GPU and CPU that helps to make up the bandwidth deficit inherent in using slower memory. So even without direct confirmation, we now knew that the 8GB of memory in Xbox One is indeed DDR3 as opposed to the bandwidth-rich GDDR5 found in the PlayStation 4 (and Wired's internal photography of the One confirms 2133MHz DDR3 Micron modules). Xbox One may well have a latency advantage over PS4 and power consumption will probably be lower, but GPU bandwidth - a key element in graphics performance - is indeed more limited on the Microsoft hardware.
In terms of the GPU hardware, hard information was difficult to come by, but one of the engineers did let slip with a significant stat - 768 operations per clock. We know that both Xbox One and PlayStation 4 are based on Radeon GCN architecture and we also know that each compute unit is capable of 64 operations per clock. So, again through a process of extrapolation from the drip-feed of hard facts, the make-up of the One's GPU is confirmed - 12 compute units each capable of 64 ops/clock gives us the 768 total revealed by Microsoft and thus, by extension, the 1.2 teraflop graphics core. So that's another tick on the Durango leaked spec that has been transposed across to the final Xbox One architecture and the proof we need that
PlayStation 4's 18 CU graphics core has 50 per cent more raw power than the GPU in the new Microsoft console. Now, bearing in mind that we fully expect PlayStation 4 and Xbox One to launch at similar price-points, how did this disparity come about?
The answer to that comes down to a specific gamble Sony made that Microsoft could not - the utilisation of a unified pool of GDDR5 memory. In the early days of PS4 development, only 2GB of this type of memory looked viable for a consumer-level device. As higher density modules became available, this was duly upgraded to 4GB. By the time of the reveal back in February, Sony had confidence that it could secure volume of 512MB modules and surprised everyone (even developers) by announcing that PS4 would ship with 8GB of unified GDDR5 RAM. The design of its surrounding architecture would not need to change throughout this process - one set of 16 GDDR5 chips would simply be swapped out for another.
Microsoft never had the luxury of this moving target. With multimedia such a core focus for its hardware, it set out to support 8GB of RAM from day one (at the time giving it a huge advantage over the early PS4 target RAM spec) and with serious volume of next-gen DDR4 unattainable in the time window, it zeroed in on supporting DDR3 and doing whatever was necessary to make that work on a console. The result is a complex architecture - 32MB of ESRAM is added to the processor die, along with "data move engines" to courier information around the system as quickly as possible with bespoke encode/decode hardware to alleviate common bottlenecks. Bottom line: if you're wondering why Xbox One has a weaker GPU than PlayStation 4, it's because both platform holders have similar silicon budgets for the main processor - Sony has used the die-space for additional compute units and ROPs (32 vs. 16 in One), while Microsoft has budgeted for ESRAM and data move engines instead. From the Xbox perspective, it's just unfortunate for Microsoft that Sony's gamble paid off - right up until the wire, it was confident of shipping with twice the amount of RAM as PlayStation 4.
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http://www.eurogamer.net/articles/digitalfoundry-spec-analysis-xbox-one
