Saturday, August 23, 2014

Samsung announces 20nm Exynos 5430, used in Galaxy Alpha

Exynos 5430 built with improved process, higher efficiency

It was recently reported that Samsung has announced the Exynos 5430 SoC, manufactured using a new 20nm process. This chip, which has strong similarities with previous generation Exynos chips such as Exynos 5420 and 5422 manufactured at 28nm, is likely to be an application processor that integrates CPU, GPU and other processing cores, but does not integrate a baseband and other RF-related interfaces like modern smartphones SoCs from Qualcomm and others.

Like Exynos 542x, the chip utilizes ARM's big.LITTLE architecture for the CPU with heterogeneous multi-processing capability (HMP), also called Global Task Switching (GTS), containing four fast but relatively power-consuming Cortex-A15 cores and four slower but power-efficient Cortex-A7 cores. HMP allows all eight cores to run simultaneously without significant restrictions (previous big.LITTLE implementations use cluster migration that only allows the use of either the A15 or the A7 cores at the same time, which is less efficient). Unlike previous Exynos chips such as 542x, actual application of HMP in practice is reported to be more feasible with the new chip.

On the GPU side, Samsung continues to use a Mali T6xx series GPU, more specifically the Mali-T628 MP6 GPU. Although reasonably fast and supporting OpenGL ES 3.x according to the specifications, this GPU is likely to be less economical (more die space) and less power-efficient than next generation Mali T7xx cores, and has seen little use outside of Samsung Exynos chips. Additionally, because this GPU core came to market before the finalization of the OpenGL ES 3.1 specification, support or performance for this standard may not be optimal. However, as long as OpenGL ES 2.0 remains the dominant API for mobile devices, this may not be very apparent to most end users.

Samsung strongly motivated to use more Exynos SoCs

Samsung has several reasons to try to increase internal SoC production for devices such as smartphones and tablets, including excess capacity in their logic fabs to due the loss of Apple application processor orders, and tight supply of Qualcomm SoCs that have recently been used in the vast majority of Samsung's smartphones.

Additionally, relying less on Qualcomm chips may reduce the effective amount of patent royalties that Samsung has to pay to Qualcomm. Although Qualcomm strives to collect significant royalties on all smartphones, its licensing policy has recently come under pressure in China and other countries, and not using Qualcomm chips may make it easier to contest royalty payments. And finally, the internal production cost of the Exynos chip (assuming reasonable yield rates) added to the selling price of Intel's modem chip, may still be lower than the price that Qualcomm asks for integrated SoCs such as the Snapdragon 800 series, since it has a virtual monopoly in that segment.

Several, but not all models of Galaxy Alpha use Exynos 5430

Samsung is reportedly using the 5430 in at least some variations of the new Galaxy Alpha smartphone. Other variations, such as models targeted at the US market, still use a Qualcomm processor. In the Exynos 5430-based models, LTE modem functionality is provided by a seperate Intel XMM7260 modem chip, which is a significant departure from Samsung´s almost exclusive use of integrated Qualcomm basebands/modems recently, and marks one of the rare occasions of Intel achieving a prominent design win for chips in smartphones.

Although Samsung in the past also announced use of an Exynos chips in selected models of the Galaxy S4 and S5, in practice these were little more than token announcements, involving negligable unit volume, and you have to go back to the Galaxy S3 and S2 for more material use of Exynos chips. However, it is likely that this time, for several reasons, Samsung is again, as it needs to be, more serious about shipping material amounts of Exynos chips in smartphones.

Technological improvements over Exynos 542x

Inside the 20nm Exynos 5430, some improvements over the previous Exynos 542x chips have been reported, other than the process feature size reduction from 28 to 20nm. The Cortex-A15 cores, infamous for relatively high power consumption, have been improved from the previous r2p4 to the more recent r3p3 revision, improving power characteristics, and likely facilitating the use of HMP. ARM already offers inherently more power-efficient developments of the A15 core, such as the Cortex-A17 and Cortex-A12, but these are relatively new and still largely untested for high volume production.

Also mentioned are additional process technology improvement in Samsung's 20nm HKMG process over 28nm HKMG, including the use of gate-last instead of gate-first for high-K metal gate formation and other improvements. Samsung is quoting a 25% reduction in power consumption from the process shrink alone, and the additional improvements may further reduce power consumption. To what extent these improvents result in good power consumption characteristics and battery life in devices such as the Exynos-powered Galaxy Alpha remains to be seen.

Risks involved, and Samsung still behind on integration

Actual yield rate, process maturity and ability for high-volume production is still unclear, with a limited planned production of one million Galaxy Alphas being reported. It is obvious that Samsung is well behind TSMC in 20nm process timing, capacity ramp, process maturity and quality, since TSMC has been ramping 20nm for several months in increasingly high volume for Apple for complex, highly integrated chips that are more complex than Exynos.

SoCs manufactured by Samsung for smartphones and tablets have generally been limited to application processors, while TSMC already has been producing more complex and technologically challenging SoCs incorporating basebands and other RF-related interfaces for quite some time in high volume for customers such as Qualcomm and MediaTek, spanning the low-end to the high-end. Although Samsung has been successful with production of application processors like the A6 and A7 for Apple, the higher amount of integration offered by TSMC improves cost and power consumption significantly is probably the major reason for Apple's recent move away from Samsung to TSMC. That said, Samsung is now shipping a new cost-effective SoC chip, the Exynos 3470, that likely has an integrated baseband.

Update: Global Task Switching utilizes all cores, Cortex-A15 clocked up to 1.8 GHz

Analysis of Geekbench results for the Exynos 5430-based SM-G850F (Galaxy Alpha) shows a multi-core performance scaling factor of about 4.66 for the largely CPU-bound JPEG Compress test, suggesting that Global Task Switching is indeed implemented so that not just the Cortex-A15 cores are utilized but the Cortex-A7 cores as well when high CPU performance is required. The results (in particular the JPEG Compress subtest, when compared with other devices using Cortex-A15) are also consistent with a maximum CPU frequency for the Cortex-A15 cores of 1.8 GHz.

Update of December 5, 2014

Making a count of Exynos 5430 vs Snapdragon 801-based models after a number of months of production should given an indication of the level of production of Exynos 5430. The following is apparent:
  • The Exynos 5430-based SM-G850F has a count of 1202, SM-G850M a count of 6, SM-G850Y a count of 50, SM-G850FQ a count of 39, SM-G850L a count of 85, SM-G850K a count of 26, SM-G850S a count of 72.
  • The Snapdragon 801-based SM-G850A has a count of 139, SM-G850W a count of 38, SM-G8508S a count of 3.
Based on these statistics, Exynos 5430-based models dominate with a share of 89% of Geekbench entries. However, the Galaxy Alpha has shipped in far smaller numbers that the Galaxy Note 4, which has at least ten times as much Geekbench entries.

Sources: AnandTech

Updated (November 2, 2014): Provide update based on Geekbench results (GTS, CPU clock speed).
Updated (December 5, 2014): Fix Geekbench result link (was pointing to Exynos 7 Octa entry), add Exynos share analysis based on Geekbench database.

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