Qualcomm seeks comeback with Snapdragon 820

Since it first announced the Snapdragon 820 at Mobile World Congress earlier this year, chipmaker Qualcomm has been parceling out the details in stages. It's an effective strategy to stay in the news since the Snapdragon 810 has fallen short of expectations and the 820 isn't expected to arrive until early 2016. Over time it has also given us a good idea of what is shaping up to be a strong comeback.

The latest news has to do with the Snapdragon 820's LTE modem. Qualcomm's competitive advantage has long been its integration of the most advanced wireless radios, and the 820 sticks with this playbook.

The chip's integrated X12 LTE modem is theoretically capable of download speeds of up to 600Mbps (Category 12) and upload speeds of 150Mbps (Category 13). In comparison, the Snapdragon 808 and 810 in the just-announced Nexus 5X and 6P, respectively, have an X10 modem that tops out at 450Mbps/50Mbps. The iPhone 6s and Samsung Galaxy S6 both rely on Category 6 modems limited to 300Mbps/50Mbps.

Qualcomm boosts data rates with two technologies: 3x Carrier Aggregation--meaning it can merge three 20MHz connections into one faster pipe--and higher-order modulation. The catch is that to reach these speeds a smartphone needs an additional transceiver chip and it only works when you are close to a cellular base station that supports this advanced modulation scheme. In practice you are unlikely to see half a gigabit or more very often, but then again networking technologies always fall a bit short of their advertised speeds.

With a couple additional antennas, the Snapdragon 820 supports 4x4 MIMO (four streams of data)--another way to boost LTE data rate--and it is the first mobile platform to support 802.11ac Multi-User MIMO (via a separate WiFi combo chip) to increase WiFi performance, assuming you have one of the so-called Wave 2 access points that support it. It is also Qualcomm's first chip to support LTE over unlicensed spectrum to augment download speeds. Verizon plans to deploy LTE-U starting next year, but it is controversial because it could interfere with WiFi traffic over the same 5GHz spectrum, and other operators are waiting until standards have been ironed out. Finally there is a separate chip that adds 802.11ad, also known as WiGig, which works only over short distances at 60GHz, but is very fast, making it well-suited for connecting to external monitors or docking stations.

The Snapdragon 820 is Qualcomm's first chip with a custom, 64-bit CPU core, known as Kryo. The chip is manufactured on an advanced 14nm process with FinFET transistors (most likely by Samsung, though GlobalFoundries is also a possibility) and the quad-core CPU is capable of reaching speeds of 2.2GHz. Qualcomm says it will deliver up to twice the CPU performance of the current Snapdragon 810, which uses four ARM Cortex-A57 cores and four A53 cores. Not including Intel's Atom line, only two other mobile processors are widely available at this advanced node: Samsung's 14nm Exynos 7420 and the Apple A9, which according to recent teardowns uses both Samsung's 14nm process and TSMC's 16nm alternative.

Qualcomm hasn't said much about the Adreno 530 graphics, except that it will be 40 percent faster than the Snapdragon 810's Adreno 430 GPU. We know more about the other big core inside the Snapdragon 820, the Hexagon DSP (Digital Signal Processor). Qualcomm originally designed DSPs to power its cellular modems, but over time these have taken on other specialized processing tasks that they can handle more efficiently than general-purpose CPUs. The Snapdragon 820 includes three types of DSPs: a Modem DSP with a single-core (four threads) Hexagon 5xx, a Low Power DSP with a single-cluster (two threads) Hexagon 6xx that powers the system's "always-on" sensors, and a Compute DSP based on the new Hexagon 680.

At the Hot Chips conference last month, Qualcomm's Lucian Condrescu talked about the 680's new Hexagon Vector Extensions (HVX) for image and video processing, computer vision, augmented reality and VR headsets. In addition to two scalar clusters--each with two threads running at 500MHz for a total of 2GHz scalar performance--the Hexagon 680 has two 1,024-bit wide vector processing units for fixed-point arithmetic. Codrescu showed some Qualcomm test results indicating that a Snapdragon 820 with HVX provides several times better performance than a 32-bit ARM quad-core CPU with ARM's NEON SIMD instructions on image processing and computer vision tasks. The other interesting feature of the HVX units is that they can intercept the incoming raw data from a device's camera and clean it up before passing it on the new Spectra image processor for further processing.

The real benefit of having all of these different cores in the Snapdragon 820, according to Qualcomm, comes from heterogeneous processing. This is another way of saying that the system is smart enough to figure out which cores can complete a given task in the fastest and most efficient manner. Plenty of other chip companies are working on this. MediaTek has its CorePilot, and AMD and others have the Heterogeneous Systems Architecture (HSA). But Qualcomm claims that by designing everything from the ground up, it can more efficiently allocate tasks to the Kryo CPUs, Adreno GPU, Hexagon DSPs and image and video processing blocks. Interestingly, although Qualcomm was one of the founding members of the HSA, there's no mention of it and they seem to be doing their own thing with the Snapdragon 820 (next week I'll be at the Linley Processor Conference where we should hear more about progress toward using HSA in real products).

Qualcomm will continue to have lots of competition at the high end. MediaTek's X20 with 10 CPU cores (one cluster of Cortex-A72 cores and two clusters of four Cortex-A53 cores) is slated to show up by the end of the year; HiSilicon is already shipping its 16nm Kirin 930 octa-core with faster versions, the Kirin 940 and 950, on the way; and there are rumors that Samsung has developed a custom core, code-named Mongoose, for the next Exynos. But it is hard to see how any of these companies--or Intel, for that matter--will be able to match the combination of wireless technology and heterogeneous processing performance in the Snapdragon 820 platform. Perhaps that's why there's already talk that Samsung will revert to using Snapdragon in more versions of the Galaxy S7. Time will tell whether the Snapdragon 820 delivers, but it certainly looks strong on paper.