Cortex-A73 CPU and Mali-G71 GPU power up next-gen phones

Computex 2016 - At its Computex press conference this morning, ARM announced two new pieces of mobile SoC IP that it believes will drive the demanding applications that smartphone owners will want to run on next-generation devices. The company says 4K gaming, VR, and augmented reality will all increase the performance demands on mobile SoCs. ARM is rising to this challenge with the Cortex-A73 CPU and the Mali-G71 GPU.

The Cortex-A73 CPU core is claimed to deliver 30% more performance than ARM's previous high-end core, the Cortex-A72, while improving power efficiency by up to 30% over the older design—at least, when it's fabricated on a 10-nm process. The A73 core doesn't deliver this improvement by becoming a wider machine. Indeed, ARM says the chip is a two-wide design, as opposed to the A72's three-wide front end. Instead, the company suggested that a blend of process and architectural improvements will let the chip hit higher peak clocks—up to 2.8GHz, as opposed to the A72's 2.5GHz—and extract more performance from features like an improved branch predictor.

Where the A73 may really shine is in applications like games and VR that require sustained performance from the SoC. Past high-end mobile SoCs have been tailored to handle "bursty" workloads, where a user might run a demanding application for a short time and then perform less-demanding tasks the rest of the time. VR, AR, and gaming applications offer the chip no such relief: it has to run flat-out for long periods without overheating.

The more-efficient A73 core is designed to specifically address this problem. One of ARM's slides suggests the A73 core has basically eliminated the delta between peak and sustained CPU performance in certain tasks. On a simulated Spec2K benchmark, a 2.8GHz, 10-nm A73 is claimed to deliver 1.3 times the peak performance of a Cortex-A72 and 2.1 times the peak performance of a Cortex-A57. The A73 also delivers this performance in a smaller die area than past ARM cores: just 0.65 mm2. That small area makes room for SoC designers to add more resources like GPU cores to their chips.

ARM has some new GPU IP for those chip designers to play with today, too. The Mali-G71 GPU core is claimed to deliver some impressive performance improvements over ARM's previous high-end GPU core, the Mali-T880. The company says the G71 is up to 50% faster than the T880, and it purports to deliver 20% better energy efficiency, 40% better performance density, and 20% more bandwidth than that older part even when it's fabricated on the same process. G71 is also more scalable than the T880. Implementations of this GPU can include up to 32 shader cores, up from 16 in the older part.

The Mali-G71 is the first GPU to use ARM's next-generation Bifrost architecture. Bifrost gives the G71 support for the Vulkan low-overhead graphics API. It can also take advantage of a fully-coherent system interconnect to DRAM to enable heterogenous computing. From a chip-layout perspective, Bifrost also purports to reduce the number of "wirelets" needed to connect shaders, a move that ARM claims has a positive impact on performance, as well.

ARM already has a number of partners signed up for the A73 and G71 IP, including Hisilicon, Huawei, Marvell, Mediatek, and Samsung. The company says we should expect to begin seeing SoCs with Cortex-A73 cores and Mali-G71 GPUs in devices around the end of this year or in early 2017.

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