Multi-core processors are becoming the go-to differentiator for smartphone OEMs. Consumers have been conditioned by desktop and laptop marketing to understand that two is better than one; who wants to be sitting flat-footed with a single-core smartphone while a dual-core heavyweight is available?
But is it all just a marketing ploy or are there real benefits to multi-core application processors?
Stuart Robinson, director of the handset component technologies service for Strategy Analytics, says the multi-core boom is the result of marketing and innovation. “Part of it is marketing. It’s great to have the ‘dual-core inside,’ if you like. But part of it is performance benefit of dual-core, and performance limitation with single core.”
Robinson says that the clock frequency of single core processors is limited in smartphones because of space constraints; even Apple hasn’t managed to design a fan or a heat sink into the smartphone.
“If you go above about 1 gigahertz, 1.2 gigahertz, then the power dissipation is too big and the phone overheats and burns a hole in your pocket. So in order to do that, if you split the processing functionality across two cores, and you run them both at half speed, you get roughly the same performance and the power dissipation is kept down,” Robinson explains.
So the 1 GHz dual-core should be like running a 2 GHz single-core, right? Not quite. Robinson explains that the complications of running two cores, including conflicting code running on either cores, can lead to an overhead in terms of the splitting of processing power across two cores. But the multi-core smartphone still gets along at a bit higher speed than does its single-core predecessors.
“Typically, we say that if you’ve got two cores running at 1 GHz, it’s equivalent to about 1.7, 1.8 gigahertz single core. Not quite as good as 2 GHz,” he says.
Will the end user see an uptick in the speed at which applications run over a dual-core processor? Robinson says yes, but adds that some of the current single-core devices remain very competitive, citing as an example the single-core processor that powers the Sony Ericsson Xperia Play. “I asked them when they launched [the Xperia Play] in Barcelona, which dual-core chip are you using? And they said, no, it’s just a single-core… and I thought that’s amazing, the performance you can get even from a 1 GHz chip.”
Robinson says about eight smartphones are on the market right now that run dual-core processors, including the Atrix 4G, Droid Bionic, LG Optimus 2X, Optimus 3D, among others, but this is just early times. “Everyone is getting on the dual-core bandwagon,” Robinson says.
Take it from an Expert
Qualcomm, which develops its own processors from scratch, is heavily invested in dual-core technology. The company licenses the instruction set from ARM, but then implements those instructions using customer processors and custom logic, to the power performance perfect on each core.
Raj Talluri, vice president of product management for Qualcomm CDMA technologies, says his company’s attention to detail is the reason the Snapdragon processor has seen the kind of traction it has. “We’ve been able to run at over 1.4 GHz, whereas other companies had to push the voltage much higher to get there and even then our power numbers are much lower.”
Qualcomm’s dual-core approach is unique from what others in the industry are doing in that Qualcomm allows each core to run at separate speeds. Talluri says most companies restrict the cores to running at the same speed. The result is more efficient performance and less battery drain.
Talluri says that the need for dual-core is simple: “As the demand for applications increases, you just need more performance and you have to come up with other ways to do it.”
So why not just keep adding cores? If two is better than one, then four must be better than two. Talluri says to some extent that’s true, but it’s a little more complicated than “more is better.” Many applications are still single-threaded, which means that at any given time, the application is only running one execution track. You can’t really break up that thread across two cores.
“So, going from one core to two cores helps, and in some applications going from two cores to four cores helps, but going beyond that will help if the software, like operating systems and the applications, start getting more and more multi-threaded,” he says. “Not all applications can become multi-threaded, so there’s a little bit of diminishing returns.”
Much is made around the effective use of power in dual-core handsets, with many users reporting less than desirable battery life on newer dual-core handsets. Talluri says battery technology itself is getting better but that until there’s major evolution, a lot of the advances that will make a difference in battery life for end users are coming on the chipset side of things.
“When you are running a video clip, we actually turn everything else of,” Talluri says, which leads to some pretty complex system checks before any task is completed or killed. But that’s where Talluri says most of the gains in battery efficiency are to be had, in managing that complexity, which he says Qualcomm is uniquely positioned to handle.
“That’s why when you make a full system, like when you make the processor, the power management, the RF, the Bluetooth, the modem, like we do at Qualcomm, we’re able to control the power to each of those blocks. These are really complex systems, not just the processor,” he says.
Before the Storm
This is the quiet before the multi-core storm. Strategy Analytics recently forecast 15 percent dual-core penetration in smartphones by the end of the year, with an estimated 45 percent penetration by 2015.
Further rollouts of next-generation networks will only further necessitate the need for more powerful processors, but until then, consumers looking to re-up their contract with a new smartphone have a choice to make. Verizon Wireless currently offers only three LTE-capable smartphones, none of which are dual-core.
Talluri says that’s just a matter of what was available when OEMs started designing those phones and says that the next crop of 4G phones will almost certainly include some multi-core entrants.
“The new ones that are coming out will clearly be dual-core. Our latest chip, the 8960, is our most efficient applications processor, which is dual-core and also has LTE integrated inside it,” Talluri says, adding that the battery life will be a whole lot better on phones with those chips.
So will all the dual-core fun only be had by the high-end superphone users? Talluri says it’s just matter of time before this high-end technology trickles down.
“I believe that a fairly high percentage of phones will be dual-core…When you start optimizing your software on the high end, these are features people are going to want on the middle and low end as well,” Robinson says.