Apple, Samsung Usher in the 20nm, 64-bit Smartphone Generation

By Michael J. Miller

It's taken longer than we would have originally expected, but it looks like the 20nm generation of application processors for smartphones is beginning to appear, powering the Apple iPhone 6 and 6 Plus, as well as some versions of the Samsung Galaxy Note 4 and Note Edge, due out shortly.

When it announced the iPhone 6, Apple said it would be powered by a new processor, the A8, manufactured at 20nm and that it would be Apple's second 64-bit processor, following the A7 which debuted in the iPhone 5s.

Apple's Phil Schiller said the new processor has 2 billion transistors, compared to 1 billion on the A7, but the A8 is 13 percent smaller because of the move to 20nm. He said that it has 25 percent faster CPU performance and 50 percent faster graphics than the A7 used on the iPhone 5s. But beyond that, he didn't give many details.

That's normal for Apple, but usually once the devices ship, third parties take the chip apart and examine it to give us more details. For the A8,Chipworks has the first real details, and has worked with Anandtech to make some educated guesses as to the features of the chip.

The A8 die measures 89 mm2, compared with 104 mm2 on the A7. Chipworks says it appears the chip is manufactured on TSMC's 20nm process, as had been widely rumored, instead of the 28nm Samsung process used by the A7. It still is a dual-core processor, and the CPU cores appear to be an enhanced version of the Cyclone cores used in the A7, both based on the ARMv8 64-bit instruction set. Graphics have been enhanced as well, likely to the Imagination Technologies' PowerVR GX6450, which still has four GPU cores, although with other improvements.

Chipworks notes that some of the structures inside the chip, notably the 4MB of SRAM memory, didn't shrink by the 50 percent you would normally expect for each node—if everything followed Moore's Law exactly. But still the chip is 13 percent smaller than the A7, despite Apple's claims of nearly doubling the number of transistors. Given that the core counts for the CPU and GPU remain the same, and the amount of SRAM cache seems to have also stayed constant, it seems likely that Apple used the additional transistors for more features, to improve performance and to make the chip more power efficient. Indeed, at the announcement, Schiller said the chip was up to 50 percent more energy efficient and was designed to offer more sustained performance.

Note that Apple has control of the operating system and the processor, so it could create a 64-bit version of iOS to accompany the 64-bit processor. But the 64-bit quality isn't being used to allow more main DRAM memory in the devices (as 32-bit processors would only allow a 4GB memory space). Chipworks and Anandtech suggest that the iPhone 6 has only 1GB of memory, compared to the 2 or 3GB of memory in most high-end phones. But the ARMv8 64-bit instruction set just seems to be more efficient.

Meanwhile, it appears that Samsung is shipping a version of the Galaxy Note 4 with a 20nm 64-bit processor in some markets. At the announcement, Samsung said there would be two versions of the phone—one with a 2.7GHz Qualcomm Snapdragon 805, which is the version we'll get in the U.S., and one with a Samsung Exynos 5433 with cores running at 1.9 and 1.3 GHz.

Samsung's chip business has announced the Exynos 5 Octa 5430 applications processor, which is manufactured on Samsung's 20nm process, with four 1.8GHz Cortex-A15 cores and four 1.3GHz Cortex-A7 cores in a big.LITTLE configuration. This is a 32-bit processor, essentially a shrink of the 28nm Exynos 5422.

Anandtech says the 5433, which still isn't listed on Samsung's website, actually has four 1.9GHz Cortex-A57s and four 1.3GHz Cortex-A53 cores with ARM's 64-bit cores in a big.LITTLE configuration. As mentioned before, the 64-bit instruction set seems more powerful, and there are improved power management features, but the phone is almost certainly going to be running in a 32-bit mode, in part because the firmware and the current version of Android only support 32-bit operation. But it does move up to Mali T-760 graphics, which should improve graphics performance.

Meanwhile, Qualcomm has started shipping 64-bit chips in its Snapdragon 610 line, including the Snapdragon 615, which is used in theHTC Desire 820. The Snapdragon 615 has four 1.5GHz ARM Cortex-A53 and four 1GHz Cortex-A53 cores, but again the phone is running in 32-bit mode because of the state of the firmware and operating system. These chips are manufactured on TSMC's 28nm process.

Qualcomm's first 20nm chip is slated to be the Snapdragon 810 with four 64-bit ARM Cortex-A57 CPU cores running at up to 2 GHz and four Cortex-A53 cores, along with faster graphics and an integrated LTE Category 6 modem. This is expected to be sampling shortly and due in products in the first half of 2015.

(And of course, Intel is already shipping 22nm and even starting to ship 14nm chips for Windows tablets, with the Core family supporting 64-bit, and has its 22nm Atom products for Android and Windows tablets.)

Presumably, we'll see Android L shortly as well, which promises real 64-bit support for the Android ecosystem. So after a lot of waiting, it looks like the era of 64-bit, 20nm applications processors is dawning for smartphones, and tablets can't be far behind either.