MediaTek makes it official: New Helio X20 packs 10 cores, three CPU clusters

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Last week, we reported on rumors that MediaTek was preparing to launch a new 10-core chip dubbed the Helio X20. Today, we can confirm those rumors are accurate. The Helio X20 will pack an unprecedented 10 CPU cores in a single die and connect the entire framework with MediaTek’s first custom interconnect, the MediaTek Coherent System Interconnect (MCSI). The chip will have three core clusters — one pair of Cortex-A72s clocked at 2.5GHz, one quad-core set of Cortex-A53s at 2GHz, and one quad-core Cortex-A53 cluster clocked at 1.4GHz.


MediaTek makes it official: New Helio X20 packs 10 cores, three CPU clusters

A second major first for MediaTek is the launch of the company’s own modem technology. MediaTek hasn’t revealed much about its modem to date, but it’s claiming support for up to Cat 6 LTE. The tri-cluster CPU is going to be the headline topic, however, and when we discussed the X20 last week, we were dubious of whether MediaTek could wrangle 10 CPUs into delivering a performance benefit.

According to MediaTek, building more levels of big.Little (ARM shot down the idea of big.Little.Littlest when we asked) is to emulate the automotive industry and create more gears for better shifting. This comparison is slightly problematic. While it’s true that adding more gears to a transmission can definitely increase fuel efficiency, simply slapping more gear ratios into a pre-existing vehicle is the wrong way to do it. It’s increasingly common to see vehicles with 6-8 gears, but the entire assembly has to be redesigned to make certain that the gains outweigh the increased weight and parasitic energy loss. The gains themselves are fairly small — according to extensive federal testing, an eight-gear transmission delivers just 3% better fuel economy in combined tests compared with a 5-speed (page 70/129).

MediaTek, however, is claiming better figures than the modest improvements from higher transmission gearing. The company showed data that projects a 15-40% power consumption improvement from using three core clusters instead of two, though it did not state whether the chips were compared apples-to-apples, or if the dual-core clusters were 28nm CPUs compared with tri-core on 20nm. MediaTek is also integrating a Cortex-M4 onboard CPU for ultra-low power operation and audio processing offload. This type of task-specific work can definitely improve battery life in workloads that leverage the embedded processor.
Can MediaTek put it all together?

I don’t want to sound overly dubious about MediaTek — in the past, I’ve praised the budget manufacturer for launching itself into the smartphone and tablet industry and taking on larger, more established players. The inconvenient truth, however, is that wringing better power efficiency and overall performance out of silicon is difficult. It’s taken ARM years to get big.Little properly patched and integrated into Linux, and even today we’ve seen some companies ship devices with old or out-of-date power management subsystems. The same fragmentation that haunts Android in other contexts can damage it here, as well.

The Helio X20 compared to its predecessor, the X10.

It’s not clear if ARM’s existing Global Task Scheduler can properly address MediaTek’s triple-cluster implementation or if the SoC designer has committed to doing custom work to ensure that its handset and tablet partners will be able to take full advantage of the chip’s load-switching capabilities. Heck, it’s not even clear that Global Task Scheduling is all that effective in smartphone and mobile devices, given that high-powered cores can soak the thermal envelope of a modern phone within seconds. It’s entirely possible that thermal limits will prevent MediaTek’s 10-core behemoth from ever activating more than a fraction of those chips.

One thing is certain: MediaTek is setting a very high bar. The company is clearly pushing to establish itself as a major player in the mainstream and even premium smartphone and tablet categories. I may be dubious about the usefulness of a 10-core SoC, but MediaTek clearly wants to be perceived as a contender for the design spaces Qualcomm is used to winning. The Helio X20 isn’t set to debut until December 2015, however, which means MediaTek could face significant competition from 14nm Exynos products and Qualcomm designs. Rumors of a MediaTek-AMD collaboration, meanwhile, remain unproven.

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