The iPhone 5’s New A6 Isn’t Quad Core, But...

When Apple announced the iPhone 5, the company also rolled out the new A6 System on a Chip (SoC). Not a lot is known about the A6 yet, but one thing was noticeably absent from the September 12 presentation: any mention of the term “quad core.” There might be good reason for that.

The smartphone business is ultra competitive. Other smartphone makers are touting the move to quad core CPUs, and it was expected that Apple would have to appear to be keeping pace. And yet, Apple has been noticeably mum on that aspect of the iPhone 5.

In contrast, in the past, Apple has been eager to identify the core configuration of the iPhone 4S (dual core) and the new iPad/iPad 3 (dual core with quad core graphics.)

iPhone 5 Configuration

The iPhone 5 analysis starts with the fact that Apple’s presentation claimed a 2x improvement across the board compared to the A5. The question is, how did Apple achieve that?

The consensus right now is that Apple is the first company to commercially deploy the Cortex dual core A15 processor. This is a very advanced, efficient chip based on a 32 nanometer process.  Manufactured by Samsung, it uses High-k Metal Gate (HKMG) technology. Clock for clock, it’s said to be 40 percent faster than the older Cortex A9 used in the A5 in the iPhone 4S.

What’s being speculated about is how the Cortex A15 is being utilized to achieve that 2x gain. With an appropriate increase in the clock speed, say another 40 percent, from 800 MHz to 1.12 GHz, Apple could achieve a total factor of about two in performance, just as the company has claimed. However, increases in clock speed are a means of last resort, something to be avoided in consideration of heat and battery life.

One reason to suspect that route, mentioned by Andrew Cunningham, is that most iOS apps are designed to support two cores and would have to be recoded to take advantage of more cores.

A second, different approach argues that an increase in clock speed can be avoided by using two dual core A15s. Anand Lal Shimpi, who is very astute about CPU architectures, wrote “Based on the performance gains, Apple's history of SoC naming and some other stuff we've heard recently, it looks like Apple has integrated two ARM Cortex A15 cores on Samsung's 32 nm LP HK+MG process.” That is, four total cores, but not classic quad core.

A hint that Apple may have used that configuration is that Apple’s performance slide (above) shows only Apple apps, those that could have been specially tuned for 4 cores in advance.

In either case, there is no direct use of what one would call a classic quad core architecture. And so Apple apparently decided to deflect any discussion of the number of cores in order to avoid criticism that they’re not keeping up with the quad core competition. At a basic consumer level, perceptions can be formidable in marketing and in those pervasive comparison charts.

On the other hand, Apple would want to pick the best technology, optimize power consumption, and be mindful of the architecture of typical iOS apps, and so quad core may not be the preferred choice in 2012 based on best overall performance.

Soon, we’ll find out more details when the A6 is fully dissected.


Image Credits: Apple

TMO's Jim Tanous contributed to this article.