Xbox One readies shift to 20nm – but can a smaller node help it match the PS4’s performance?

Ever since the Xbox One and PS4 were unveiled as being based on 28nm technology, it’s been clear that both Microsoft and Sony would transition to smaller nodes as soon as those technologies were ready for prime time. It now looks as though Microsoft may make this jump before its rival. A sharp-eyed member of the Beyond3D forum picked up on the LinkedIn profile of one Daniel McConnell, an SoC designer at AMD, which discusses how he, “Successfully planned and executed the first APU for Microsoft’s Xbox One game console in 28nm and a cost-reduced derivative in 20nm technology.”

So what could it mean for Microsoft’s console to make a quick jump down to 20nm? In theory, such a shift could give Microsoft several advantages. Power consumption and die size both come down modestly at 20nm, which improves yields and price structure. The system chassis could theoretically be redesigned with new features or MS could target a cheaper model with certain capabilities removed. In the past, both Microsoft and Sony have used these periodic revisions to target modest improvements to storage capacity, performance, peripheral hookups, or other similar options.

The current Xbox One SoC – a 28nm APU made by AMD

But I think there’s an interesting question here, that strikes at the concept of what a console actually is and what Microsoft can or can’t get away with doing. For decades, consoles have been presented as fixed units. Sure, the external shell and some of the I/O hookups might change over time, but an Xbox 360 purchased in 2005 should be just as fast as an Xbox 360 bought in 2014. Consoles have been inviolate, even as PC hardware shifts fairly rapidly.

As Microsoft looks at its plans for a 20nm die shrink, it has to be asking if there’s a way to change the Xbox One’s design to better match the PS4. And it probably can — as we’ve previously discussed, there are two unused GPU partitions on the system that would give it a significant GPU performance boost. It might also be able to increase the size of the shared ESRAM cache.

The problem, though, is optics. Early adopters of the Xbox One can’t be particularly pleased that they bought a now-useless doorstop in the form of Kinect 2.0. No one is going to be happy if Microsoft rolls out a new version of the Xbox One (Xbox 1.5?). And the company would risk bifurcating its dev teams between haves and have-nots. For a company whose message has already been badly diluted and confused, the presence of two different types of console would be problematic at best. Furthermore, McConnell’s profile makes it clear that Microsoft chose to drive engagements that would minimize costs over increasing performance in future iterations of the SoC.

Xbox One internals [Image credit: iFixit]

We’ve toyed with the idea of upgradeable consoles in other posts, but after the problems the Xbox One has had with brand and message, I think shifting the system’s design now would only confuse and frustrate users further. 20nm die shrinks are also expected to be relatively modest, with the following 14/16nm technology delivering more raw performance and the bulk of improved thermals.

What about DDR4?

One intriguing option Microsoft might take would be to outfit the console with DDR4. There’s been a great deal of discussion over whether or not the Xbox One’s quad-channel DDR3 memory bus is a problem for most games, with some general consensus that it likely is. Microsoft could close this gap, at least in theory, by upgrading to a faster form of DDR4. 8GB of DDR4-2700 or even DDR4-3200 would improve memory bandwidth by 25-50%. The question, however, is whether games could be programmed to run equally smoothly on both sets of hardware.

Again, that’s problematic. If memory bandwidth is really the issue, Microsoft might wind up having one console that can run 1080p safely, while the other is stuck in 900p territory. Is it possible to build a resolution toggle into games? PCs certainly have done it for years, but it’s not clear if this is possible on the console side.

Microsoft could theoretically swap out the DDR3 on the Xbox One for DDR4 without changing any of the underlying specs, but I suspect this will be difficult. DDR3 and DDR4 have very different latencies and matching the two well enough to make them identical at the design level might be more trouble than it’s worth.

Source: http://www.extremetech.com