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MediaTek Adds Midrange Dimensity

New 700-Series Processors Target Sub-$300 5G Smartphones

August 17, 2020

By Mike Demler

MediaTek’s new Dimensity 700-series represents the third (and lowest) tier in its lineup of 5G-smartphone processors. The first product is the Dimensity 720 (D720), which targets phones selling for less than $300—a step below the mid-premium ($300–$500) Dimensity 800-series and two steps below the flagship Dimensity 1000. The new processor integrates the same cellular modem as the D800 and D820, but it clearly differentiates from those higher-price models by greatly reducing performance.

TSMC manufactures all Dimensity processors in its 7nm technology. It quickly ramped that process, enabling MediaTek to offer significant upgrades from the Helio P65, a 12nm midrange processor it introduced last year. The P65 powers BBK and Samsung 4G phones that sell in the D720’s target price range. The new chip adds 5G support, along with substantial improvements in all the compute subsystems. Like its predecessor, it employs a 2+6 CPU configuration, but it replaces the P65’s “big” Cortex-A75s with higher-performance Cortex-A76s. The process shrink allows the GPU to go from a two-core Mali-G52 to a three-core Mali-G57, and it permits the addition of a new AI accelerator.

The new chip is in production; it appears in 5G versions of Oppo’s A72 smartphones, which sell in China for 1,899 yuan (about $270). Huawei and Xiaomi also plan to develop D720-based phones, and we expect Samsung will do so as well. The MediaTek processor will compete with Qualcomm’s Snapdragon 690, which should enter volume production later this quarter. LG, Motorola, Sharp, TCL, and other companies plan to offer 690-powered phones.

Big CPU and GPU Upgrades

The Dimensity 720 combines two Cortex-A76 and six Cortex-A55 CPUs, as Figure 1 shows. Despite the process shrink, the big A76s run at the same 2.0GHz clock frequency as the A75s in the Helio P65 (see MPR 7/29/19, “Helio P65 Upgrades Midrange Phones”). But judging by Geekbench scores for A75- and A76-based MediaTek chips, the latter core provides 34% more single-core performance than the former. The A55s run at 2.0GHz as well—18% faster than in the Helio P65. According to our CPU metric, overall performance increases by 28%. The chip also integrates an always-on sensor hub, which detects keywords for multiple voice assistants. The wake-word detector includes a DSP that supports dual-microphone noise suppression.

Figure 1. Dimensity 720 smartphone platform. MediaTek’s new midrange chip includes a sub-6GHz 5G modem. It also upgrades the CPU, GPU, and AI accelerator from the previous-generation Helio P65.

The GPU gets an even bigger boost than the CPUs by employing three Mali-G57 cores, which appear in the mid-premium Dimensity 800-series as well (see MPR 2/24/20, “MediaTek Brings 5G to Mid-Premium”). The D820 has five G57 cores and the D800 has four. According to the company, the G57 scores 40fps on the GFXBench Manhattan 3.0 Offscreen test—twice the performance of the earlier Mali-G52 MC2. Like the 800-series, the D720 connects to two 16-bit LPDDR4X-4266 DRAM channels.

The new design includes a small AI accelerator, primarily for enhancing camera functions, but it omits the more powerful tensor accelerator of the D800 and D1000. The company withheld architectural details, but on the basis of performance, we expect the chip has the same Cadence Vision P6 cores as the Helio G90T (see MPR 8/19/19, “MediaTek Helio G90 Ups Its Game”). These cores provide a total of 512 integer multiply-accumulate (MAC) units to deliver about 800 billion operations per second (GOPS).

As in the Helio G90T, the Vision P6 works with the ISP to enable face unlock and computational-photography features such as bokeh. The ISP can handle a single 64-megapixel (64MP) camera or split its capabilities to support a 16MP+20MP dual-camera configuration. The video engine can encode or decode 4K-resolution content at 30fps. The 720 drives HDR10+ screens of up to 2,520x1,080 resolution, the same as its predecessor, but it boosts the refresh rate from 60Hz to 90Hz.

Not Quite a World Modem

Dimensity processors work with sub-6GHz 5G networks but not millimeter wave (mmWave). But it’s a nonissue in most markets outside North America, the only region with significant mmWave deployment. According to Counterpoint Research, MediaTek’s RF front end (RFFE) handles six 5G bands between 1.8GHz and 4.5GHz, constituting fewer than half of the sub-6GHz bands. Nevertheless, that capability covers most 5G operators in Asia, Australia, Europe, and Japan, as well as AT&T and Sprint/T-Mobile in the US.

The baseband supports two-channel carrier aggregation (2xCA), LTE+5G dual-connectivity (EN-DC), dual SIM/dual standby (DSDS), and Voice Over New Radio (VoNR). The peak downlink speed on 100MHz of 5G spectrum is 2.3Gbps, and the peak uplink is 1.3Gbps. But using its EN-DC capabilities, the modem can aggregate a 20MHz channel in the 1.8GHz LTE band and a 100MHz channel in the 3.5GHz 5G band, for example, increasing the downlink speed to 2.8Gbps. Dimensity processors can also boost coverage and throughput by anchoring the uplink on low-band FDD while employing high-band FDD and TDD aggregation for the downlink.

The modems improve power efficiency using MediaTek’s UltraSave technology. On light workloads, UltraSave trims power by reducing transmission bandwidth. It supports 3GPP Release 15’s bandwidth-part (BWP) adaptation, dynamically adjusting the modem’s operating frequency and power configuration by monitoring the network conditions and data-transmission quality. Other connectivity features are the same as in previous Dimensity chips: 802.11ac Wi-Fi with 2x2 MIMO, Bluetooth 5.1, and GNSS.

Lowering the Bar for 5G Gamers

In 2Q20, 5G smartphones constituted one-third of all handsets sold in China, according to Counterpoint Research. Rapid 5G adoption in that populous country has driven MediaTek and Qualcomm into a fierce battle to extend 5G capabilities to lower-price phones. Huawei and Samsung develop their own SoCs for mid-premium and flagship phones, but they employ third-party chips for most midrange models.

Like MediaTek, Qualcomm has three 5G-enabled product tiers: the Snapdragon 800-, 700-, and 600-series. The Snapdragon 690 holds a substantial edge over the Dimensity 720 in several performance metrics, allowing it to target slightly higher-price mid-premium phones (see MPR 6/29/20, “Snapdragon 690 Lowers 5G Entry Price”). Nevertheless, it’s the D720’s closest competitor.

As Table 1 shows, the D720 and Snapdragon 690 integrate similar 2+6 CPU configurations, but the latter provides 24% greater single-thread performance (thanks to its big Cortex-A77 cores) as well as 10% greater multithread performance, according to our CPU metric. But the D720 will appeal more to 5G gamers. MediaTek aims to deliver graphics performance similar to that of the Helio G90T, which integrates a previous-generation Mali-G76 GPU. At 40fps on the GFXBench 1080p Manhattan 3.0 test, the D720’s Mali-G57 beats the Adreno 619L by roughly 20%, by our estimate.

Table 1. Mainstream 5G-smartphone processors. The Dimensity 720 and Snapdragon 690 both aim to bring 5G capabilities to mainstream phones. They offer comparable modem speeds, but Snapdragon delivers much greater AI performance, and its ISP triples Dimensity’s resolution. *Relative to 1.0GHz Cortex-A9 across several mobile benchmarks; excluding CPU and GPU. (Source: vendors, except †The Linley Group estimate)

The Snapdragon 690 offers much greater AI acceleration and camera resolution than the Dimensity 720. Its primary AI engine is a Hexagon 692 DSP that includes a tensor accelerator, which delivers more than three times the throughput for neural-network inference. Qualcomm’s ISP provides superior premium-camera capability, handling 192MP image sensors, although midrange phones will use that capability for 32MP+16MP dual cameras rather than a single high-resolution one. The D720 supports 20MP+16MP dual cameras, adequate for the sub-$300 market.

Qualcomm is the only smartphone-chip vendor to implement mmWave 5G, but few operators (and none in China) require that capability. The D720 and Snapdragon 690 provide similar downlink speeds on sub-6GHz networks, but MediaTek claims a 2x uplink advantage. The chips deliver the same speeds on LTE networks. Qualcomm supports the latest 802.11ax Wi-Fi standard (Wi-Fi 6), whereas MediaTek supports 2x2 MIMO using the older 802.11ac, which is adequate for sub-$300 phones.

Driving 5G Into the Mainstream

Consumers are reluctant to plunk down $1,000 or more for a shiny new 5G phone. In the mid-premium segment, however, sales in China have grown rapidly. Some 5G handsets are already selling there for less than $300, but by offering its new D720, MediaTek aims to drive 5G handsets further into the mainstream tier. Chinese phone buyers appear eager to take advantage of the 100MHz of spectrum in China Mobile’s 2.5GHz band, as well as the 200MHz in China Telecom’s and China Unicom’s 3.5GHz band.

Qualcomm also aims to proliferate 5G into lower-price phones, but its Snapdragon 690 targets more expensive models than the D720 does. Although sub-$300 phones don’t have 192MP cameras, OEMs looking to support AI applications will prefer the Hexagon-based accelerator to the D720’s anemic 0.8-TOPS engine, which is only useful for face unlock and other basic features. The MediaTek product offers similar 5G speeds and superior GPU performance relative to the Qualcomm chip, yet it saves die area by integrating smaller Cortex-A76 CPUs and omitting a large AI accelerator, enabling it to undercut the 690 in price.

Besides the 5G modem, the D720 boasts considerable upgrades from the company’s previous-generation midrange processor: in CPU and GPU performance as well as in camera features. The modem omits mmWave and doesn’t support as many sub-6GHz bands as Snapdragon’s X51 modem, but it’s sufficient to address most markets that the Helio P65–powered phones cover, including Asia, Australia, Europe, and Japan. In the US, it works with all operators except Verizon. Nevertheless, the lowest-price 5G phone available there sells for about $600. The Dimensity 720 will help reduce 5G-smartphone prices in the US as well as in other regions.

Price and Availability

MediaTek withheld pricing for the Dimensity 720, but we expect the chip to sell for about $20 in high volume. It’s in production now and is shipping in Oppo’s 5G A72 smartphone. More information on the new chip is at www.mediatek.com/products/smartphones/dimensity-720.

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