Differentiation comes two ways. ARM designs different chip models with different architectures -- like the A8, A9, and A15 chips -- each more capable than its predecessor.
As a starting point, says Samsung's Nick DiCarlo, vice president of product planning, you have to compare the architecture of each chip when comparing SoCs. A single-core A9 chip (also called Cortex-A9) will dominate a single-core A8 chip, and so on.
Modifications are a second way that chipmakers differentiate and fine-tune their product's performance. Nvidia's claim to fame is a lower-powered fifth core on its Tegra 3 quad-core processor, which handles low-power tasks like background app updates and has the ability to control how many cores run at a time.
The path to even better performance, says Qualcomm's Raj Talluri, vice president of product management, is getting a license to custom-build a CPU core based on ARM's raw instruction set and managing everything from design of the entire ARM-based system to the final production.
"We're able to get more performance with two processors than our competition can get with four," he bragged of Qualcomm.
Although Talluri didn't say it outright, at the time, he could have been defending HTC's decision to use Qualcomm's Snapdragon S4 dual-core processor on the HTC One X in the U.S. and Nvidia's quad-core Tegra 3 processor elsewhere.
For its part, Nvidia bought licensing rights for ARM's faster A15 chip in 2011 and are already coming to light. (More rumors .)
Myth No. 2: Doubling the chip doubles the performance
You double the number of chips when you evolve from single-core to dual-core and from dual-core to quad-core, but what you're not doubling are the rest of the resources. All cores still must share a single battery and pool of memory.
If the entire system is efficient (more on that later), Qualcomm's Talluri told me, you will see increased performance. Just don't expect said performance to actually double when you migrate from a comparable dual-core chipset to its quad-core fellow.
Myth No. 3: All cores, all the time
The assembly line analogy to explain how four cores speed up processes on your smartphone is handy, but incomplete. That's because no matter how many cores you have, there's only so much they can share tasks without the help of software.
First, the operating system itself has to support "multithreading"; that is, assigning each processing core a chunk of a task. The device manufacturer also gets into the game, adding some software layers to help the hardware and operating system communicate.
I spoke to five experts in the course of preparing this article, and they all emphasized the need for the developers who actually program the apps and games to code with multithreaded execution in mind.
The problem, says Greg Sullivan, senior product manager for Microsoft, is that writing code to take advantage of multiple processor cores makes writing apps much harder. Likewise, there's a lot more complexity in debugging apps when something goes wrong, a challenge that many app developers are reluctant to face.
Gaming and video are two examples of many apps that can take advantage of multiple threads. Let's say you want to stream a video clip from YouTube or ESPN. Video streams aren't easily broken down. According to Sullivan, video spools in a serial process, it doesn't easily divide up for multiple cores to work on and then reconvene. As a result, some tasks, like watching a video, will max out one of the cores while the other core or cores update apps in the background, pull in e-mail, and so on.
Sullivan's take on video is up for debate. Chipmaker Nvidia claims that its Tegra 3 processor can efficiently make use of its multiple cores even if the apps themselves aren't threaded, and codecs do exist to thread video streams.
Either way, all signs point to even better core performance with apps that are specifically designed for multicore use.
Myth No. 4: More cores save battery life
Many CNET readers have shared with me their skepticism that more cores will save battery life, believing instead that quad-core phones will drain a battery faster.
Although it isn't always the case, they have a reason to doubt.
The car engine analogy was a favorite with the experts I spoke with for a very simplified way to explain what happens with power. GHz (as in a 1.5GHz processor) are like RPMs, and more processor cores are like more cylinders. More cylinders give you more engine power, but at the cost of guzzling gas.
The smartphone's display, CPU (that's the application processor we've been talking about), and the cellular radio suck up the lion's share of the battery. There's a Catch-22 when it comes to performance. Faster CPUs let us accomplish more tasks in a shorter period of time -- rendering images smoother, connecting to the Internet faster -- but they also demand more juice.
Nvidia, however, points out that their chip's fifth smaller core fits into the analogy differently.
"When the car is in city traffic and does not require the high performance engine, the high performance engine is turned off and only the electric engine is used," said a company representative. "When the car is on a freeway, then one to four cores are used depending on the desired speed."
The increased demand on the battery during times of high-level performance (like streaming Internet video, for instance) is exactly why system-level optimization is so important, said Frances Sideco, senior principal analyst of consumer and communications at the analyst firm IHS iSuppli.
Engineers on the manufacturing side can be smart about creating software that can help efficiently assign processor tasks, which in the end mitigates battery strain and could help make the battery-saving theory of quad-core a reality (where more chips each doing part of the work drain the battery more slowly.)
Nvidia's Tegra 3, for instance, boasts system-level optimizations that can turn cores on and off depending on which tasks need to be done.
On top of that, some chips will be inherently more efficient than others (see myth No. 1.) Battery life is an ever-present issue, and the chip makers that can produce the most battery-balanced systems will see slower battery drain for the same task.
Myth No. 5: The CPU stands alone
HTC blew me away with photo rendering in the One X, One S, and One V that was . I mean, it was really, really fast. HTC points to its own image processing chip.
The more you can free up the application cores from having to perform certain resource-heavy tasks, the more they can focus on quickly updating your Facebook status and downloading a podcast.
That's why today's system-on-a-chip includes peripheral cores built around the ARM processor, like the graphics processing unit (GPU), any image processors like HTC's, video and audio units for encoding and decoding, and Flash processors. And guess what? The performance of these separate modules all add up to affect the entire system as a whole.
Myth No. 6: Don't forget the operating system
Right now, quad-core mania is centered on the Android OS, though the iPhone 5 and Windows Phone OS are currently capable of supporting two or more cores.
Not too long ago, the single-core/quad-core divide was a pain point for Microsoft, which had them leaning hard on its "" campaign, which pits a Microsoft employee on a Windows Phone against Android and iPhone users to see whose phone performs simple tasks faster.
Now that enabled dual-core processing for phones like the and , the point is no less important: we should evaluate performance based on real-life tasks, and not on theoretical benchmarks.
In the real world, said Microsoft's Sullivan, performance rests on how efficiently the operating system can manage tasks, period. One advantage that Sullivan points to is Windows Phone's behavior to suspend apps when you switch focus, rather than run them in the background and take up cycles and power to do so.
Of course, Microsoft may sing a different tune now that it's shipping its own multicore phones, though I suspect that Android phones will long be ahead in the game of processor one-upsmanship.
However, Microsoft's Sullivan isn't alone in his approach. Qualcomm's and Samsung's VPs, and the IHS iSuppli analyst I spoke with all echoed Sullivan's main sentiment, that the way the operating system manages threads of code and processes in general affects the phone's overall performance, no matter the number of cores.
Myth No. 7: Benchmarks don't lie
Samsung's Nick DiCarlo has a strong opinion about chip performance benchmarks. He explained that most processor performance tests measure dozens of elements of the chip, including subcategories of optimization.
Yet, 30 separate and highly specific measurements aren't often useful, especially when manufacturers have a range of chips to report on and compare.
Aggregating the results with benchmark tools offers a shortcut. Diagnostic apps that calculate benchmark performance for the GPU, CPU, and browser can be useful indicators, but like all statistics, they're also ripe for manipulation.
"Can they be exploited?" DiCarlo offered, "Definitely."
What's to come
The rise of quad-core smartphones began in 2012 and will grow in 2013 for flagship phones. They'll even start becoming mainstream, as chip makers like Nvidia, Qualcomm, Samsung, and others continue to aggressively push the release cycle and help market the processor as a larger part of the purchasing decision.
While I'm just as excited to see ever-faster chips lead to ever more powerful smartphones, it's worth remembering this: quad-core isn't automatically faster in every case, and more cores aren't always better.
Smartphones Unlocked is a monthly column that dives deep into the inner workings of your trusty smartphone.