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SC9863 Is First Cortex-A55 Octa-Core

July 3, 2018

Author: Mike Demler

Octa-core chips using two quad-Cortex-A53 clusters have been the industry standard for sub-$150 smartphones, but Unisoc (formerly Spreadtrum) is the first to build such a low-cost chip using one Cortex-A55 cluster. The SC9863 employs Arm’s DynamIQ architecture, which allows heterogeneous combinations of up to eight CPUs. To handle high-performance tasks, it runs four A55s at a 1.6GHz clock frequency, but less compute-intensive tasks run on four power-saving cores that operate at a maximum 1.25GHz. The company plans to begin volume production in 3Q18.

The SC9863 is Unisoc’s fourth octa-core processor. Two years ago, the company introduced the Cortex-A53-based SC9860, its first chip manufactured in a 16nm FinFET process. Its second-generation octa-core chips took a big step up in performance by switching to Intel’s Airmont CPUs and 14nm technology. According to our CPU performance metric, the SC9861G-IA delivers 63% more CPU performance than the SC9860, thanks to its dual-issue architecture and 2.0GHz speed for all cores. The SC9853I runs at a 10% slower frequency than the SC9861, and it targets lower-price phones.

Although the SC9863 uses newer Cortex-A55s, it delivers the same CPU performance as the SC9860. Unisoc expects the A55s to score 18% higher on the SPECint2006 benchmark, but the new processor runs its four performance cores at a 20% slower frequency than in the SC9860, eliminating the performance gains.

It lacks a dedicated deep-learning accelerator (DLA), the SC9863 gets a big boost in convolutional-neural-network (CNN) performance thanks to the new Arm v8.4-A dot-product instructions. Since dot products are the most frequent calculation in CNNs, Arm made these instructions an option in its Neon SIMD extensions for the Cortex-A55, Cortex-A75, and Cortex-A76. Unisoc employs them for computational photography and computer vision.

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