Setting Up the Mobile CPU Battle of 2016
Setting Up the Mobile CPU Battle of 2016
When earlier this week ARM introduced its new CPU and graphics cores, as well as a new interconnect to connect these together and to memory, it did more than just present the next step in its popular cores that get used in mobile application processors. ARM also set up many of the parameters by which next year’s mobile chips will be judged.
The heart of the announcement is the company’s new Cortex-A72 processor, ARM’s third 64-bit processor. This is intended to be the next step beyond ARM’s current high-end Cortex-A57, which is just beginning to appear in high-end application processors. In most implementations to date, we’ve seen A57 cores paired with ARM’s lower-end Cortex-A53, which uses much less power for less demanding workloads, often in 4+4 configurations, notably including the Qualcomm Snapdragon 810(slated for the forthcoming LG G Flex 2) and the Samsung Exynos 7 Octa 5433 (used in some versions of the Galaxy Note 4).
Like the A57, the new A72 cores are also expected to be paired with A53 cores in ARM’s big.LITTLE scheme. (Recall that ARM licenses intellectual property such as cores to a variety of vendors, who then use these to create specific chips. Here are overviews of the building blocks chips that were in the market for last year. I’ll update these posts for 2015 after we see more chip announcements, likely at Mobile World Congress next month.) The A72, A57, and A53 all use the 64-bit ARMv8 instruction set, and can support 64-bit Android 5.0 Lollipop.
ARM says the A72 will have a number of advantages over the A57, particularly if used as targeted on the next generation of process technology. ARM says that compared with an existing 32-bit Cortex A15 core on 28nm technology, an A57 core on 20nm should provide 1.9 times the sustained performance at the same smartphone power budget, but the A72 can provide 3.5 times the performance of the A15. It’s not quite another doubling each year, but pretty close. Alternatively, to handle the same workload, it could use 75 percent less energy, and with the big.LITTLE design, ARM claims an average reduction of another 40-60 percent. In short, it should prove to be a big boost in either power or performance, depending on what you are doing. Of course, in a typical design with both big and little cores, you would expect that the little cores will be used the vast majority of the time, with the big cores used only for demanding tasks such as game play or web page rendering.
The Cortex-A72 is designed for mobile processors that will be manufactured on 16nm and 14nm process technology using 3D FinFET transistors. So one question is how much of the performance gain is the result of the new A72 design and how much simply comes with the more advanced process. Previously, TSMC said its 16FF+ (16nm FinFET Plus) design would offer a 40 percent speed improvement or a 55 percent power reduction over its 20nm design. So obviously the process technology is important, though it appears that the design changes help as well. And ARM’s announcement also included new IP designed to make it easier for chip designers to move to the TSMC 16FF+ node, allowing Cortex-A72 implementations to run at up to 2.5GHz.
In addition to the CPU, the company announced a new high-end graphics core called the Mali T-880, which ARM says can provide 1.8 times the performance of its current high-end Mali-T760 (used in the Exynos 7 Octa) or 40 percent less energy at the same workload; and a new cache-coherent interconnect, called the CoreLink CCI-500 designed to link the CPUs and other cores together, allowing twice the peak system bandwidth (important for 4K resolution) and increasing the speed by which memory connects to the CPU. There are also new cores for processing video and handling displays. ARM said a single Mali-V550 video processor can handle HEVC encoding and decoding, and an 8-core cluster can handle 4K video at up to 120 frames per second.
In its announcement, ARM said it had already licensed the A72 to more than 10 partners, including HiSilicon, MediaTek, and Rockchip. HiSilicon primarily makes the Kirin line used in parent company Huawei’s smartphones, while MediaTek and Rockchip are merchant vendors. According to the announcement, the new cores are slated to appear in final products in 2016.
Of course, many other vendors will offer alternatives by then. Samsung has traditionally used ARM cores, so I wouldn’t be surprised if it uses the A72/A53 combination in a future chip. Alternatively, Qualcomm has said it is working on a follow-up to the Snapdragon 810 that will use custom CPU cores based on the ARMv8 architecture, much as its Krait 32-bit cores were used in its high-end application processors. And Apple uses custom CPU cores based on the ARM architecture in its chips, and transitioned to the 64-bit architecture for the “Cyclone” core for the A7 used in the iPhone 5s and more recently introduced a new version for its A8 processor in the iPhone 6 and 6 Plus and A8X used in the latest iPad Air.
Meanwhile, Intel has its SoFIA line of chips based on the Atom core due out in 2015, and plans a new 14nm version for 2016, along with a higher-end chip known as Broxton.
It looks like the targets for 2016 will be more CPU and GPU performance within the power envelope of a typical smartphone, while consuming lower power when performing most tasks. I’ll be interested to see at Mobile World Congress and beyond what the specific chip designers have to say about how their chips match or beat ARM’s claims here.
malikmuddser