Mobile Mania Redux

When will we stop talking about SoC architectures for mobile devices? Probably never.

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By Frank Ferro
As I prepare to hit Barcelona for Mobile World Congress, I get the feeling that this will be a ‘do-over’ of last month’s CES, only without all the HD and 3D TVs. Although wireless infrastructure and applications are a big part of MWC, at the device level, tablets and smartphones will continue to dominate all the discussions. Déjà vu, anyone? Yet the reality is we are in the early generations of these products, and especially from the perspective of the underlying SoC technology, we are just starting to scratch the surface of this multi-dimensional tech discussion.

In last month’s blog, I looked at the critical role of the SoC as an enabling technology and how device manufacturers need a strong SoC strategy to stay relevant. I am in no way discounting the value that OEMs bring in differentiating their products at the device level (we have all come to know and love Apple). However, by taking responsibility for driving SoC architectures it will ensure that these OEMs will continue to differentiate with better features and at a lower cost, making all of us consumers happy.

So let’s review some of the SoC device and system requirements to determine what will be necessary to keep these mobile markets hot…and getting even hotter.

How fast is fast? The first and seemingly most interesting question is how fast does the SoC have to run? The real answer to the question is almost moot because the default answer is: The faster you can run, the better. Of course I understand that in mobile systems, speed and power consumption need to be intricately balanced. However, we are now—especially with the tablet architecture—at a speed inflection point of moving from single-core, 1GHz processors to multicore processors with up to 4 cores and even a 5th core for low-power running at speeds of 2GHz+.

I say the speed question is moot for several reasons. As the process technology shrinks (28nm and below), there is increased space on the die for more processors. This is not only true for the CPU, but the GPU is now rivaling the CPU in die area. Clearly device manufacturers want to take full advantage of all this processing power allowing for speed ‘margin’ in the design. This margin gives designers the peace of mind knowing that the SoC will have the longevity needed to keep up with all the latest and multi-tasking applications now prevalent in tablets and smart phones. And finally at a very practical level, having extra speed provides the SoC designer the margin needed to ensure that they can close timing at the target speed!

It really is all about bandwidth. Given the increased speed of the processors, we now need to look at how this will affect the rest of the system. The first and most obvious place to start is the memory subsystem. Without a properly designed memory subsystem, there will be no way to utilize all the available processing power. Wide I/O memory is emerging as one solution to the SoC bandwidth problem. Although Wide I/O memory is not without its manufacturing challenges, from an architectural perspective it offers the necessary increase in bandwidth by utilizing four channels (in the first generation) of DRAM memory. This increased bandwidth also comes with the advantage of having a lower-frequency memory interface, along with reduced power consumption, because the memory is connected directly to the SoC die using TSV technology.

To maintain bandwidth, it is also important to have a high-performance on-chip network that can support the high speed and connectivity requirements between the processors and memory. For example, with processors running at 2GHz, the network must be able to operate with margins at 1GHz to keep pace with the processors. It is vital for the network to support ‘load balancing’ of the traffic flowing to the four channels of memory to ensure maximum DRAM utilization.

It’s the total system. Without a doubt, the speed and memory performance are key components of an SoC that are helping to drive the technology forward. To move the technology and end-products to the next level, however, it will require a broader integration of not only the SoC hardware (the stage we are today), but also the integration of the SoC with the OS and applications. Of course this is easier said than done, given the limited number of companies that are vertically integrated. And even the ones that are don’t necessarily have the proper communications channels in place between hardware and software teams to effectively achieve this goal.

Looking at the SoC from the systems perspective offers the possibility of significantly optimizing applications performance and power management (for starters). We are now beginning to see application-aware operating systems, but we don’t see the link to the underlying hardware, which can offer a real breakthrough in overall system performance (AKA enhanced end-user experience).

The next level. There is clearly a lot of work to do at the SoC integration level to achieve the increased performance and bandwidth needed for the next generation of mobile devices. Keep in mind we didn’t even explore some of the custom features required for this market, such as security. The real challenge for moving the SoC platforms forward is to find the right catalyst to force teams—both hardware and software from the application level down to the lowest level hardware—to look at the problem from the total system perspective. And, fingers crossed, to finally stop focusing only on their piece of the problem.

This catalyst can emerge from a lead OEM moving the bar where all other companies will then have to oblige, or from a specific demand from the market—a new ‘must-have’ capability. Having a total systems view will allow for better coordination of hardware resources, giving the software team better access and visibility of the low-level hardware. Ultimately, setting up the triple threat demanded by consumers: Getting dramatically better performance with significantly lower power, translating to a superior user experience.

So when will we stop talking about SoC architectures for mobile devices? Perhaps when we retire…

–Frank Ferro is director of marketing at Sonics.


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