Smartphone platforms migrate to 64-bit (AArch64) mode

Recently, most existing and new mobile SoCs have started to become available configured in native 64-bit mode (AArch64) in conjuction with a 64-bit version of Android 5. Although SoCs targeting premium-level devices that are already shipping were the first to support AArch64 (including Tegra K1-64, Exynos 7420 and Snapdragon 810), recent entries in the Geekbench results database show that cost-sensitive platforms are also migrating to native 64-bit mode in upcoming smartphones.

This move involves Cortex-A53-based platforms such as MediaTek's MT6735, MT6752, MT6753 and MT6795, Qualcomm's Snapdragon 615 (MSM8939) as well as a new Snapdragon 410 (MSM8916) platform (which was previously limited to ARMv7), and HiSilicon's Kirin 620 and Kirin 930.

Initial ARMv8 platforms used hybrid AArch32 mode

Several ARMv8 based SoCs have been shipping for some time, but most have been using AArch32 mode, a hybrid mode which takes advantage of some of the architectural improvements in ARMv8 but does not expose native 64-bit mode to applications. Snapdragon 410 did not even take any advantage of ARMv8, running in 100% ARMv7 mode.

One reason why full AArch64 mode has not been adopted right away is that is does come with a performance penalty due to the increased storage requirements for program code and pointers, which puts greater demands on the memory subsystem of the SoC. Cost-sensitive smartphone models are especially sensitive to this due to a lower amount of RAM and smaller on-chip CPU caches. A decrease in the price of RAM chips has allowed the amount of RAM in cost-sensitive models to increase (e.g. more devices shipping with 2GB RAM), making AArch64 mode more appealing.

AArch64 also has benefits, in particular for floating point and data-intensive applications that use NEON vector instructions.

Comparison of CPU benchmark results

The migration to AArch64 mode across the board makes it easier to compare CPU benchmarks of different SoCs, which was previously made more difficult by the fact that some SoCs used AArch64 mode while others were still limited to AArch32.

In the following sections, I will return to Geekbench CPU test results and try to make apples-to-apples comparison for different groups of SoCs.

Quad-core Cortex-A53 SoCs

Quad-core SoCs included are MT6732, MT6735 and Snapdragon 410. Note that the version of Snapdragon 410 tested most likely reflects a newer silicon revision that has not yet widely appeared in end devices, since previous versions of Snapdragon 410 (MSM8916) were always limited to ARMv7 mode (seemingly being unable to run in AArch32 mode).

The following table shows selected integer tests results from Geekbench entries for the mentioned SoCs, running in AArch64 mode.

SoC        Geekbench  Clock  JPEG Compress (int)      Lua (int)
           ref        speed  Single IPC   Multi Par   Single IPC   Multi Par

MT6732     2705430    1.50    783   1.36  3108  3.97   795   1.29  3017  3.79
MT6735     2650175    1.30    646   1.36  2604  4.03   656   1.23  2047  3.12
MSM8916-64 2708213    1.21    626   1.34  2481  3.96   615   1.24  1280  2.08

The table below shows selected floating point and memory results.

SoC        Geekbench  Clock  Mandelbrot (float)       Stream Copy (memory)
           ref        speed  Single IPC   Multi Par   Single Multi

MT6732     2705430    1.50    631   1.23  2490  3.95  1030   1156
MT6735     2650175    1.30    526   1.19  2091  3.98   901    965
MSM8916-64 2708213    1.21    508   1.23  1969  3.88   447    505

The "IPC" value as shown in the tables is an index calculated from a comparison with the performance of common Cortex-A7-based SoCs, normalized to the same clock speed. The parallelism value ("Par") is the performance scaling from single-core to multi-core for the specific Geekbench subtest.

The IPC values are fairly consistent, as would be expected from the same CPU core (Cortex-A53) running the same ISA (instruction set architecture). When scaling to multiple cores, MT6732 does best, as shown by the scaling in the Lua benchmarks. This is not surprising as MT6732 is not an entry-level SoC given its cost structure, being better described as belonging to the mid-range segment. It is likely to have a better memory subsystem (in particular, a larger and faster L2 cache) than the other chips.

MediaTek's new entry-level chip, MT6735, apart from running at a somewhat higher clock speed (1.3 GHz vs 1.2 GHz), outperforms the 64-bit version of Snapdragon 410 when normalized to the same clock speed, which is especially evident in the Lua multi-core test and memory tests. The Lua results could be a reflection of L2 cache size and/or speed. Memory performance (based on the Stream Copy subtest) of both MediaTek chips is roughly double that of Snapdragon 410 (something which was already evident in the respective 32-bit platform results).

Mid-range octa-core Cortex-A53-based SoCs

The octa-core Cortex-A53-based SoCs targeting the mid-range segment include MediaTek's performance-oriented MT6752, the recent cost-reduced MT6753, Qualcomm's Snapdragon 615 (MSM8939), and HiSilicon's Kirin 620 (Hi6210).

These SoCs use different CPU clock speed configurations. MediaTek's MT6752 and MT6753 run all cores at the same maximum clock speed, 1.66 GHz for MT6752 and (at least in the tested device) seemingly only about 1.1 GHz for MT6753, even though Geekbench reports a maximum clock speed of 1.3 GHz. HiSilicon's Kirin 620 can run all cores up to a maximum speed of 1.2 GHz.

Qualcomm's Snapdragon 615 uses a pseudo-big.LITTLE, hierarchical architecture with one performance cluster of four cores running up to 1.65 GHz in the most recent version of the platform (previous versions ran up to 1.5 GHz), with the other power-efficient cluster running at a significantly lower clock speed. MediaTek's annnouncement of the MT6755 (Helio P10) shows that MediaTek is also transitioning to a hierarchical CPU clusters for new chips, similar to Snapdragon 615.

Having one power-optimized CPU cluster helps power efficiency for low CPU demand scenarios such as smartphone standby or light usage. The fact that Snapdragon 615 is not very power efficient, despite the low-clocked cluster, in mostly due to the low-performance 28LP manufacturing process used.

The following table shows selected integer tests results from Geekbench entries for the mentioned SoCs, running in AArch64 mode.

SoC        Geekbench  Clock  JPEG Compress (int)      Lua (int)
           ref        speed  Single IPC   Multi Par   Single IPC   Multi Par

MSM8939    2704276    1.65    837   1.32  4269  5.10   789   1.16   667  0.85
MT6752     2709869    1.69    890   1.37  6719  7.55   907   1.31  6531  7.20
MT6753     2699665    1.10?   572   1.35  4298  7.51   587   1.30  4282  7.29
Hi6210     2704356    1.20    630   1.36  3473  5.51   626   1.27  2156  3.44

The table below shows selected floating point and memory results.

SoC        Geekbench  Clock  Mandelbrot (float)       Stream Copy (memory)
           ref        speed  Single IPC   Multi Par   Single Multi

MSM8939    2704276    1.65    661   1.17  4019  6.08    512   569
MT6752     2709869    1.69    714   1.24  5637  7.89   1024  1158
MT6753     2699665    1.10?   463   1.23  3597  7.77    802   958
Hi6210     2704356    1.20    506   1.24  3419  6.76    833  1030

IPC values are fairly consistent for MT6752, Hi6210 and MT6753 (when a likely clock speed of 1.1 GHz is assumed), but Snapdragon 615 consistently shows somewhat lower IPC, possibly related to the earlier revision (r0p1) of the Cortex-A53 core used. It is also possible that, similar to what seems to be the case for the MT6753 entry used (Meizu M2 note), the actual maximum CPU clock speed is lower than the one advertised and reported to Geekbench.

Multi-core performance scaling approaches 8.0 for the MediaTek chips, which can be expected due to the symmetrical CPU cluster configuration. Multi-core scaling for Kirin 620 is lower than expected for the integer tests, especially Lua, possibly due to L2 cache performance constraints.

Snapdragon 615, due to half the cores being clocked at a lower clock speed, shows a lower scaling factor, however the Lua scaling is particularly low, the benchmark score in fact often being worse than the single-core result, while being only modestly higher in other cases. This could be due to L2 cache constraints for one of the clusters and associated synchronisation issues in the multi-threading implementation used by the Geekbench test.

Looking at memory performance, MT6752 has the highest performance, closely followed by MT6753 and Hi6210. Qualcomm's Snapdragon 615 is well behind, probably due to the older/slower interconnect bus used.

MT6753 benchmark results suggests performance issue

Even though a clock speed of 1.30 GHz is reported to Geekbench by the operating system in the MT6753-equipped Meizu M2 Note, actual Geekbench subtest results are not consistent with a Cortex-A53 core running at that clock speed. There is variability in the results between different runs, which could be caused by thermal throttling. Many of the results seem to correspond to an effective clock speed of approximately 1.10 GHz, although for some runs the score of certain tests (including JPEG Compress) does approach the level expected for a clock speed of 1.3 GHz. Most of the time however, performance is significantly lower than expected, as if the clock speed is throttled to around 1.1 GHz for long periods of time.

The lower than expected performance could be related to the manufacturing process. The MT6753 was designed with cost-reduction in mind, and may use TSMC's 28LP process which has low cost but lower performance. Qualcomm's Snapdragon 410 and 615 also use this process, limiting their performance (and in the case of Snapdragon 615 resulting in heat production). MT6753 was announced as supporting a clock speed up to 1.5 GHz, and the lower-than-expected attainable clock speed may force MediaTek to adjust the specifications for the chip if the issue is not resolved.

Sources: Geekbench browser

Updated 6 June 2015.

Battery performance based on Geekbench battery test results

A while ago, Primate Labs added a battery performance test to the Geekbench benchmark suite, which has been frequently used on this blog and elsewhere to analyze CPU processing peformance. The battery performance test gives the opportunity to better gauge the power efficiency of different CPU architectures, especially for the type of workload that the Geekbench battery test represents.

Battery test overview

The battery test is intended to be run starting from a fully loaded battery until the battery is completely run down. It appears to target a certain fixed level of CPU processing that is sustained throughout the test. In the test results, a duty cycle parameter is given for several time points, which more or less represents CPU utilization. Slower CPU cores (such as quad-core Cortex-A7-based SoCs) have a higher duty cycle percentage, while high-performance "big" cores such as Cortex-A57 and Krait-400 show a lower percentage.

In practice, most battery test results in the Geekbench database were terminated early in the benchmark process and do not give useful information. The test runs that completed a full run-down from 100% to close to 0% battery do give a usable indication of battery efficiency. The benchmark expresses battery performance as a number, similar to Geekbench CPU performance scores. This score is correlated with the duration and duty cycle using a certain formula, reflecting the amount of CPU work done and the battery running time. The score is heavily influenced by the actual capacity of the battery used in the device.

Overview of results for common SoCs

The following table shows Geekbench approximate battery test scores for common SoCs used in smartphone models for which a battery capacity specification is available. The table is ordered by SoC model name.

Device                    SoC              Score      Capacity  Duration    Score /
                                           (Range)    (mAh)     (hrs:min)   mAh

Apple iPhone 5S           Apple A7         1220-2090  1560      2:00-3:30   0.78-1.34
Apple iPhone 6            Apple A8         1550-2360  1810      2:35-4:00   0.86-1.30
Apple iPhone 6 Plus       Apple A8         2580-3250  2915      4:20-5:25   0.89-1.11
Meizu MX Pro              Exynos 5430      2080-2730  3350      7:45-10:10  0.62-0.81
Samsung Galaxy Alpha      Exynos 5430      1850-2710  1860      4:30-5:00   0.99-1.46
Samsung Galaxy Note 4     Exynos 5433      3190-3650  3220      5:20-6:00   0.99-1.13
Samsung Galaxy S6 Edge    Exynos 7420      4100-4600  2600      7:00-7:45   1.58-1.77
Huawei Honor 6            Kirin 920        1580-2080  3100      2:40-3:30   0.51-0.67
Huawei Mate 7 (MT7-L09)   Kirin 925        2470-2820  4100      4:05-4:20   0.60-0.69
Huawei P8 (GRA-L09)       Kirin 930        3270-4150  2680      5:30-7:00   1.22-1.55
Lenovo A5000              MT6582           3740       4000      14:00       0.94
Xiaomi Redmi Note         MT6592           2850-3560  3200      7:30-9:00   0.89-1.11
Huawei G750-U10           MT6592           2960-3430  3000      7:45-9:00   0.99-1.14
Meizu MX4                 MT6595           2540-2780  3100      6:20-6:55   0.82-0.90
Lenovo A7000-A            MT6752M          4550-4950  2900      8:16-8:50   1.57-1.71
Meizu M1 Note             MT6752           4900-6310  3140      8:10-10:30  1.56-2.01
HTC Desire 820s           MT6752           3580-3730  2600      6:15-6:30   1.38-1.43
HTC One E9+               MT6795           3370       2800      6:00        1.20
Moto G                    MSM8226 (SD400)  1600-2000  2070      6:00-7:30   0.77-0.97
Xiaomi Redmi 1S           MSM8226 (SD400T) 1485       2000      5:30        0.74
Lenovo A6000              MSM8916 (SD410)  2700       2300      6:50        1.17
HTC Desire 826            MSM8939 (SD615)  1800       2600      4:25        0.69
Xiaomi Mi 4i              MSM8939          2520-2810  3120      5:50-7:30   0.81-0.90
HTC One M8                MSM8974 (SD801)  2500-3300  2600      4:20-5:50   0.96-1.27
Xiaomi Mi 4               MSM8974          3150       3080      7:45        1.02
Samsung Galaxy Note 4     APQ8084 (SD805)  2500-3550  3220      4:10-6:15   0.78-1.10
LG G4                     MSM8992 (SD808)  2500-3260  3000      4:15-5:30   0.89-1.09
HTC One M9                MSM8994 (SD810)  1400-2580  2840      2:20-4:20   0.49-0.91

Devices with low processing power but long battery life may be penalized by having to power the screen and wireless connectivity for a longer period during the test.

The ratio of the battery score and the battery capacity (in mAh) gives a very rough indication of the efficiency of a particular CPU architecture, although the comparison may be skewed by several factors.

Results by SoC type

The previous generation of Cortex-A7-based SoCs such as Snapdragon 400 and MT6582 shows long running time due the effiency of the Cortex-A7 core, but the battery score appears to be affected by the limited CPU power. Snapdragon 410 does relatively well despite (or perhaps thanks to) being limited to ARMv7 mode.

SoCs with previous generation Cortex-A15 cores for performance in a big.LITTLE configuration, such as Kirin 920/925, show relatively low efficiency, as is to be expected given the relatively high power consumption Cortex-A15 is known for. Exynos 5430, which is manufactured on a relatively advanced 20 nm process, generally does better.

Octa-core mid-range: MediaTek does well

Among octa-core mid-range SoCs such as the Cortex-A53-based MT6752 and Qualcomm's Snapdragon 615 and MediaTek's previous-generation Cortex-A7-based MT6592, both the MT6752 and MT6592 make a strong showing, with MT6752 getting particularly high scores.

MT6752 has an optimized memory architecture with a 32-bit memory interface and is manufactured on TSMC's 28HPM process, which helps performance relative to Snapdragon 615. Although not tested by Geekbench, reports indicate that wireless standby power efficiency is not as great as the CPU efficiency for this SoC. It is possible that due to the CPU cores being optimized for relatively heavy CPU loads (not big.LITTLE so no cores optimized for low power consumption at low frequencies), which includes the Geekbench battery test, a low load scenario (such as reflected in standby time) produces less optimal power consumption.

Qualcomm's Snapdragon 615 (MSM8939) does relatively poorly, which can largely be explained by the assymmetric CPU configuration and lower-performance 28LP manufacturing process.

Performance segment SoCs

The poor performance of Snapdragon 810 (as illustrated by the HTC One M9) is apparent, with significant worse battery efficiency than the previous generation Snapdragon 801 and 805. Snapdragon 808, which uses a later revision Cortex-A57 core and is used inside the LG G4, does somewhat better.

Largely due to the relatively advanced manufacturing process (14 nm FinFET for Exynos 7420), Samsung's latest SoCs do well, particularly Exynos 7420 used inside the Galaxy S6. Even Samsung's previous generation Exynos 5433 appears to be well ahead of Snapdragon 810 in terms of efficiency.

A limited number of results is available for two Cortex-A53-based performance SoCs (characterized by a wide memory interface and more powerful GPU than mid-range solutions), MediaTek's MT6795 (Helio-X10) and HiSilicon's Kirin 930. Kirin 930 shows relatively good efficiency in this benchmark, possibly ahead of MediaTek's MT6795. Kirin 930 has a two-level hierarchy in which one cluster of Cortex-A53 cores is optimized for a higher and the other for a lower frequency, while in MT6795 all cores can reach the maximum frequency.

Source: Geekbench Browser (Battery search)

Updated 28 May 2015.

Smartphone and tablet processor market share in 2014

Strategy Analytics has published its yearly report detailing global smartphone application processor market share in 2014. The total market had sales of about $21 billion with robust growth of 21%. The report shows that Qualcomm continued to lead the market in terms of revenue share with 52%, followed by Apple with 18% and MediaTek with 14%. The Apple number most likely reflects an estimate because Apple does not sell its chips to third parties. In fourth and fifth place were Speadtrum and Samsung LSI. The report mentions that HiSilicon, Intel and MediaTek had bigger growth than Qualcomm in 2014.

Qualcomm's strength based on Snapdragon 800 series wins in higher-tier phones

According to the report, Qualcomm's leadership was largely based on design wins for its Snapdragon 801 and Snapdragon 805 SoCs in the higher-tier market. Examples of this include the Samsung Galaxy S5 and LG G3. However, as I have previously reported Samsung has increased its use of in-house application processors starting from the second half of 2014, culminating in the exclusive use of Exynos 7420 in the Galaxy S6 in 2015, putting pressure on Qualcomm.

Baseband share in 2014

Strategy Analytics has also published a report with details about baseband (modem) market share in smartphones. According to the report, LTE (4G) basebands accounted for 50% of cellular baseband share in 2014, and the figure is likely to increase significantly in 2015. Qualcomm led in LTE basebands, but HiSilicon, Intel, Marvell, MediaTek and Samsung also increased LTE baseband shipments.

In terms of revenues in the overall baseband market, Qualcomm, MediaTek, Speadtrum, Marvell and Intel had the top positions in 2104. Qualcomm had 66% revenue share, followed by MediaTek with 17% and Speadtrum with 5% sare. Given the product lines of the respective companies in 2014, Qualcomm's revenues are based on both integrated SoC and separate modems, while Intel's sales were mostly separate modem chips, while the other players mostly shipped a mix of integrated SoCs and modem chips.

Comparison with 2013

Comparing with the reports that Strategy Analytics issued for 2013, Qualcomm saws it baseband revenue share remain relatively stable at 66% compared to 64% in 2013. MediaTek saw its AP market share increase from 10% in 2013 to 14% in 2014, and its baseband share increased.

Tablet processor market in 2014

According to another report issued by Strategy Analytics, the market for tablet processors grew 18% in 2014 to $4.2 billion. The top-five revenue share positions were occupied by Apple, Intel, Qualcomm, MediaTek and Samsung LSI. Apple led with 27% share (which must be an estimate), followed by Intel with 17% and Qualcomm with 16% share.

Notable is the absence among the top five of traditional leaders in the Chinese white-box market such as Rockchip and Allwinner. This most likely reflects in increase in brand name tablet shipments at the expense of the white-box tablet market, the low selling prices of white-box tablet processor and the encroachment of MediaTek and Intel into that segment.

Source: Strategy Analytics (Smartphone AP market share), Strategy Analytics (cellular baseband market share), Strategy Analytics (Tablet processor market share)

HiSilicon introduces Kirin 930/935, a performance-oriented Cortex-A53-based SoC

Huawei has introduced the Huawei P8 and P8max smartphones, featuring the Kirin 930 and Kirin 935 SoCs from Huawei's  HiSilicon semiconductor division. The octa-core Kirin 930 SoC is a performance-oriented SoC featuring only Cortex-A53 CPU cores. With a maximum clock frequency in excess of 2.0 GHz, it bears similarities to MediaTek's MT6795, but the use of a pseudo big.LITTLE configuration (four Cortex-A53 cores clocked up to 2.0 GHz and four Cortex-A53 cores clocked up to 1.5 GHz, for a total of eight cores) is reminiscent of Qualcomm's midrange Snapdragon 615 SoC, which runs at lower clock frequencies.

Huawei also introduced high-end models of both the P8 and P8max with larger storage capacity featuring the Kirin 935 SoC, which is a higher-clocked version of Kirin 930. The Huawei P8max is a smartphone with an unusually large 6.8" display.

SoC is targeted at performance-oriented devices

The Huawei P8 models are higher-priced performance-oriented smartphones, and the characteristics of the SoC match this segment. Apart from the high maximum clock speed of the Cortex-A53 cores, the external RAM interface is likely to be a dual-channel 32-bit configuration like previous performance-oriented SoCs from HiSilicon. Presentation materials from Huawei describe the Cortex-A53 cores in the faster cluster of four CPUs as being of a special, performance-enhanced type, which probably reflects the application of ARM's PoP core-hardening technology whereby the core is optimized for running at a specific frequency and a particular power profile, trading performance against die size. The process technology used is likely to be TSMC's proven 28HPM process.

The SoC is reminiscent of MediaTek's recently introduced MT6795 (Helio-X), which also targets the performance segment with an octa-core Cortex-A53 CPU configuration. MediaTek's SoC has been reported to have been adopted by competitors of Huawei such as HTC and Xiaomi.

Previous generation Mali-T628 MP4 GPU used

Rather than using an updated current-generation GPU like Mali-T760, the specs sheet for the P8max indicates the Kirin 930/935 SoCs continue to use the Mali-T628 MP4 GPU that was previously used in the Kirin 920 SoC. This GPU core is not known for great power efficiency, although there are suggestions that the more efficient Mali-T760 (which features memory bandwidth optimizations) has a relatively high silicon area and cost.

HiSilicon's new SoC line-up uses only Cortex-A53 CPU cores

Apart from Kirin 930, HiSilicon has also introduced the Kirin 620 SoC, which is an octa-core Cortex-A53 based SoC for the cost-sensitive segment, clocked up to 1.2 GHz and with a single-channel memory interface. This means Huawei now has in-house Cortex-A53-based SoCs suitable for most of its smartphone product range.

Sources: Huawei (P8 announcement), Huawei (P8max announcement), AnandTech (Huawei P8 announcement article)

Updated 17 April 2015.

Cortex-A53 based SoCs: MT6735 shows up, power efficiency of MT6752 in question

More and more devices with Cortex-A53-based SoCs, mainly targeting the entry-level and mid-range segments, are coming into the market. Qualcomm's original Snapdragon 410 (MSM8916) has already shipped in large volume, and devices using Qualcomm's Snapdragon 615 (MSM8939), as well as MediaTek's MT6732 and MT6752, have also ramped up. Meanwhile, Huawei is introducing devices using its in-house HiSilicon Kirin 620 SoC.

In the Geekbench database, results for new SoCs that are not yet shipping in end products are showing up, including MediaTek's delayed performance-oriented MT6795 (Helio-X) and the appearance of a result for the MT6735, MediaTek's new offering for the cost-sensitive segment.

In this post, I will be examining updated benchmark results for these SoCs, as well as taking a look at battery life benchmarks. Power efficiency of Cortex-A53-based products does not appear to be as good as hoped, with significant variability present (for MT6752-based devices, for example).

Snapdragon 410 smartphone platform appears to be slightly updated

Qualcomm's Snapdragon 410 (MSM8916) smartphone platform, which has performance flaws probably associated with the use of an early-revision Cortex-A53 core, seems to have been slightly updated in some recent models and reference designs, with a minor performance improvement due to a slightly higher clock speed (1.21 GHz vs 1.19 GHz) and what appears to be somewhat improved memory performance, while still being limited to 32-bit ARMv7 mode.

This improvement could be the result of a new revision of the SoC with a few hardware tweaks and an associated reference design, although it does not appear to be a radical redesign that would, for example, upgrade the Cortex-A53 core to allow use of the ARMv8 instruction set. Qualcomm's modem-less stand-alone version of Snapdragon 410, APQ8016, does appear to be a new design that does not have the restrictions of the smartphone SoC and can run in full 64-bit mode (it targets development boards and tablets).

MediaTek's MT6735 shows up in Geekbench

A single result for MediaTek's MT6735  SoC has appeared in the Geekbench database. The MT6735 is MediaTek's much-needed offering for the entry-level market with integrated LTE modem with world-mode support. It has been described as a cost-down version of the MT6732, which is a quad-core Cortex-A53-based SoC with a Mali-760 MP2 GPU. The MT6735 downgrades the GPU to a Mali-720 (probably Mali-720 MP4) which appear to be associated with lower manufacturing cost.

The MT6735 has an upgraded r0p3 revision of the Cortex-A53 core which, according to Linux kernel commits by ARM, fixes a few hardware errata which might improve performance and efficiency over previous revisions. The Geekbench entry shows the MT6735 running at a maximum clock speed of 1.3 GHz, which is lower than the 1.5 GHz of the MT6732. This could be due to the use of the cheaper 28LP process at TSMC, instead of the higher-performance 28HPM.

Notably, the device is running in full AArch64 mode, which has pros and cons for performance, but is unusual for a cost-sensitive platform because those platforms are usually sensitive to the higher demands on the memory subsystem from the increased addressing size and addressing space in AArch64 mode. Those platforms until recently only used AArch32, the 32-bit variant of the ARMv8 instruction set. The use of AArch64 makes comparisons a little difficult because it affects different benchmarks (including different Geekbench subtests) in different ways. The Android version (5.0) is also different from most existing entries for comparable SoCs, which use Android 4.4.4.

MT6752's power efficiency average, with high variability

According to most reviews that have appeared for MT6752-based devices such as the Meizu M1 Note and other devices, power-efficiency and battery life is generally average, with significant variability between devices. The Cortex-A53 core, although delivering higher performance, clearly seems to be associated with reduced power efficiency as compared with Cortex-A7 in SoC such as MediaTek's MT6582 and Qualcomm's Snapdragon 400, which generally have excellent battery life.

The variability in MT6752 performance could reflect variable performance yields in the manufacturing process, with some chips performing better (with lower voltage and power at a given frequency) than others. Frequently, chips are separated into speed bins and lower-performing ones may be sold as a cost-reduced variant running at a lower maximum clock speed. Indeed, a review of the Acer Liquid Jade S containing the MT6752M, which is likely from the poorest-performing speed bin of the MT6752, reports relatively poor battery life and some heat production. This suggests the variability may be quite large.

Update (21 May 2015): Recent information suggests that CPU power efficiency for this SoC is relatively high when CPU power is demanded, but standby efficiency (including wireless network standby) may be less impressive.

Overview of Geekbench results for Cortex-A53-based SoCs

The following tables show Geekbench results for a recent, representative entry for each Cortex-A53-based SoC. The first table below gives an overview of the devices, with SoC, CPU configuration, device model, Geekbench reference number, Android version and the instruction set architecture tested.

SoC                       CPU configuration                  Device               Geekbench Android Arch
                                                                                  reference version
Snapdragon 410 (MSM8916)  4 x 1.19 GHz Cortex-A53r0p0        Samsung SM-G360F     2275416  4.4.4   ARMv7
Snapdragon 410 (MSM8916)  4 x 1.21 GHz Cortex-A53r0p0        Xiaomi 2014817       2181099  4.4.4   ARMv7
Snapdragon 410 (MSM8916)  4 x 1.21 GHz Cortex-A53r0p0        Motorola Moto-E2     2275732  5.0.2   ARMv7
Snapdragon 615 (MSM8939)  4/4 x 1.50/1.0 GHz Cortex-A53r0p1  Samsung SM-A700FD    2274606  4.4.4   AArch32
MT6732                    4 x 1.50 GHz Cortex-A53r0p2        Elephone P6000 O2    2265175  4.4.4   AArch32
MT6735                    4 x 1.30 GHz Cortex-A53r0p3        "bq DENDE"           2268728  5.0     AArch64
MT6752                    8 x 1.69 GHz Cortex-A53r0p2        Lenovo P70-A         2276814  4.4.4   AArch32
MT8752                    8 x 1.69 GHz Cortex-A53r0p2        CUBE T7 (tablet)     2078854  4.4.4   AArch32
MT6795                    8 x 1.95 GHz Cortex-A53r0p2        Alps k6795v1_64_op01 2076054  5.0     AArch64
MT6795T                   8 x 2.16 GHz Cortex-A53r0p2        Unknown              2188071  5.0     AArch64
Kirin 620 (Hi6210)        8 x 1.20 GHz Cortex-A53r0p3        HUAWEI Che2-L11      2269931  4.4.2   AArch32

The Geekbench version used in the entries is 3.3.2 or 3.3.1.

Snapdragon 410-based devices are still limited to ARMv7 compatibility mode. Unusually for a cost-sensitive platform, the MT6735 test device uses AArch64 mode instead of AArch32 mode. Both the MT6735 and HiSilicon's Kirin 620 use a more recent version of the Cortex-A53 core, revision r0p3.

Integer subtest results

The following table shows results for integer subtests from Geekbench.

           CPU          JPEG Compress            Dijkstra                 Lua
                        Single IPC   Multi Par.  Single IPC   Multi Par.  Single IPC   Multi Par.
MSM8916    4 x 1.19      591   1.29  2379  4.03   816   1.09  2122  2.60   614   1.26  2229  3.63
MSM8916    4 x 1.21      602   1.29  2416  4.01   830   1.09  2182  2.63   632   1.27  2267  3.59
MSM8916    4 x 1.21      599   1.29  2404  4.01   739   0.97  2159  2.92   592   1.19  2168  3.66
MSM8939    4 x 1.50 + 4  832   1.44  4962  5.96   942   1.00  3469  3.68   744   1.21  2360  3.17
MT6732     4 x 1.50      842   1.46  3357  3.99  1035   1.10  3049  2.94   740   1.20  3049  4.12
MT6735     4 x 1.30      650   1.30  2563  3.94   712   0.87  1856  2.61   642   1.20  1902  2.96
MT6752     8 x 1.69      954   1.47  5810  6.09  1153   1.08  4817  4.18   850   1.22  2244  2.64
MT8752     8 x 1.69      952   1.46  7527  7.91  1200   1.13  4168  3.47   829   1.19  2294  2.77
MT6795     8 x 1.95     1026   1.37  8071  7.87   992   0.81  3886  3.92  1051   1.31  8075  7.68
MT6795T    8 x 2.16     1128   1.36  8991  7.97  1054   0.78  4159  3.95  1112   1.25  4159  3.74

AArch64 mode as used for the MT6735 and MT6795/MT6795T results has a significant influence, with the IPC (throughout per CPU cycle) for the JPEG Compress and Dijkstra tests being reduced when compared to AArch32 mode, while the IPC of the Lua test appears to be better in AArch64 mode, at least for the MT6795.

The MT6735 scores lower than the MT6732 in the Lua subtest, especially multi-core, even when correcting for the lower clock speed, which is probably the result of a smaller or slower L2 CPU cache inside the MT6735, which is targeted at the entry-level segment. The Dijkstra results are also lower, but that is probably mainly due to the use of AArch64 mode, which imposes a significant penalty on the results of this test.

Finally, while earlier results for the MT6795 showed very impressive Lua multi-core throughout, the result for the recent MT6795T entry is significantly lower (although still respectable). This is possibly due to a smaller L2 cache size in the latest revision of the MT6795T, although other reasons cannot be ruled out.

Memory and floating point subtest results

           CPU           Stream Copy  SGEMM        SFFT         Mandelbrot
                         Single Multi Single Multi Single Multi Single IPC   Multi
MSM8916    4 x 1.19      551    655    258   536   316    1264    450  1.11  1796
MSM8916    4 x 1.21      505    615    267   515   322    1292    456  1.11  1819
MSM8916    4 x 1.21      424    518    247   517   320    1277    451  1.09  1810
MSM8939    4 x 1.50 + 4  581    651    255   678   425    2510    583  1.14  3442
MT6732     4 x 1.50     1000   1187    343   697   430    1728    586  1.15  2329
MT6735     4 x 1.30      944   1034    322   636   403    1574    526  1.19  2102
MT6752     8 x 1.69     1007   1115    375  1123   485    3894    662  1.15  5279
MT8752     8 x 1.69      891   1045    387  1162   486    3902    662  1.15  5280
MT6795     8 x 1.95     1296   2070    484  1536   629    5021    824  1.24  6350
MT6795T    8 x 2.16     1380   2129    543  1847   687    5565    912  1.24  7171
Hi6210     8 x 1.20      575    996    262   819   343    2098    468  1.14  2842

The results show the memory performance advantage of MediaTek's Cortex-A53-based SoCs remains, scoring significantly higher than Qualcomm's existing SoCs, probably due to the use of a faster internal interconnect bus.

The first entry for Snapdragon 410 (MSM8916) running at 1.19 GHz is a Samsung SM-G360F, which appears to use relatively high-clocked memory, increasing memory performance over standard configurations (not listed). The two devices with a 1.21 GHz configuration have different memory performance, with the Moto G2 4G scoring lower than the Xiaomi device, probably due to the use of slower RAM. An impact from the use of Android 5 on the Moto G2 cannot be ruled out.

Sources: Geekbench browser, GSMArena (Acer Liquid Jade S review)

Updated 16 April 2015.

A detailed comparison of Cortex-A53-based and other SoCs using Geekbench, and impact of AArch64

More Cortex-A53 CPU core-based SoCs have recently come to market and more benchmark results are now available, for example from the Geekbench results database. Firmware is also becoming more mature. This makes it possible to make better comparisons between different Cortex-A53-based SoCs (for example, octa-core SoCs) and compare the performance of the highest-performance chips with competitive chips that use more expensive CPU cores such as Krait 400 and Cortex-A57.

Overview of Cortex-A53-based SoCs

The following is a list of Cortex-A53 CPU core-based mobile SoCs that have appeared in the market or for which benchmark results have become available. All chips integrate 4G LTE modem functionality unless otherwise noted.

• Snapdragon 410 (MSM8916), utilizing four early Cortex-A53r0p0 cores. Numerous cost-sensitive smartphones now use this chip. However, none of them appears to take any advantage at all of the new ARMv8 instruction set, with all of them running in ARMv7 compatibility mode. This is counter-intuitive because AArch32 (32-bit version of ARMv8), which is used by the other SoCs, already brings significant benefits. Snapdragon 410 generally perform significantly worse than other Cortex-A53-based SoCs, even when correcting for the low clock speed. This is also reflected in memory performance. The Adreno 306 GPU tends to be even a little slower than the Adreno 305 GPU in Snapdragon 400. The net result is a chip that is not much faster than Snapdragon 400 in many cases while having worse battery life.

• Snapdragon 615 (MSM8939), equipped with an octa-core Cortex-A53r0p1 CPU configuration with four cores running (in practice) at 1.54 GHz or 1.50 GHz and four cores running at a lower maximum clock frequency (probably 1.0 GHz). This chip has appeared in an increasing number of new smartphone models. Runs in AArch32 mode. Performance is significantly lower than MediaTek's octa-core Cortex-A53-based SoCs, which can run all eight Cortex-A53 cores at the maximum frequency. Memory performance is improved from Snapdragon 410 but falls short of that of MediaTek's SoCs. The Adreno 405 GPU is fairly competitive, suitable for a mid-range SoC, although the 32-bit RAM interface of the SoC limits performance, especially at high resolutions. It is manufactured used TSMC's lower performance 28LP process. There have been reports that the chip gets hot with intensive use and requires throttling.

• MediaTek MT6732, with an quad-core Cortex-A53r0p2 CPU configuration running at a maximum clock speed of 1.5 GHz. Devices using the chip are starting to become available, and tablets with the tablet version of this chip (MT8732) have also been announced. Although it has only four CPU cores, it has good performance, beating Snapdragon 615 in single core performance at a similar clock speed, and memory performance is significantly higher. The Mali-T760 MP2 GPU contributes to better GPU performance than previous MediaTek chips targeting cost-sensitive segments, although falling short of that of Snapdragon 615 and MT6752. A tablet version of the chip exists as MT8732.

• MediaTek MT6752, featuring an octa-core Cortex-A53r0p2 CPU configuration with a maximum clock frequency of 1.69 GHz. Several devices have come to market using this chip, including the Meizu M1 Note. Performance is excellent, with high scores in the Geekbench CPU benchmark, considerably higher than Snapdragon 615 and beating high-end SoCs such as Snapdragon 801 in several metrics. The Mali-T760 MP2 GPU is clocked higher than that of the MT6732, resulting in good GPU performance, comparable to that of Snapdragon 615, as measured with GFXBench, although the 32-bit memory interface will be a bottleneck at high resolutions. Manufactured using TSMC's high-performance 28HPM process. A tablet version of the chip exists as MT8752.

• MediaTek MT6795, with an octa-core Cortex-A53r0p2 CPU with clock speed up to 2.16 GHz. With a dual-channel memory interface and high resolution support, this SoC targets a higher performance segment than the previously mentioned chips, for which it can potentially offer much better performance/dollar because of the small die size of Cortex-A53 cores. Originally announced as become available in commercial devices before the end of 2014, it was delayed but competitive benchmark scores for what appears to be more mature versions of the chip have recently shown up. It appears to be configured with full AArch64 mode. Performance is excellent, with single-core performance closing much of the gap with the high-end Snapdragon 801, while multi-core performance is significantly higher. There appears to be a "Turbo" version running the CPU up to 2.16 GHz, while the regular version clocks at 1.95 GHz. At the MWC on 2 March 2015, MediaTek apparently rebranded the MT6795 as Helio X10.

• MediaTek's MT6735 is a SoC for entry-level smartphones for which benchmark results have not yet become available. It has a quad-core Cortex-A53 CPU configuration and a Mali-T720 GPU, a downgrade from the Mali-T760 GPU in MT6732. The recently announced MT6753, with eight Cortex-A53 cores running up to 1.5 GHz, is compatible with the MT6735 and also has a Mali-T720 GPU (probably MP4). Other chips that have shown up in product announcements include the MT8161 (probably the equivalent of the MT6735 without modem) and MT8165 (equivalent to MT8732 without modem).

• Qualcomm has announced additional octa-core Cortex-A53-based chips, Snapdragon 415 and Snapdragon 425. These probably utilize symmetrical Cortex-A53 configuration with all cores running at the same maximum clock frequency, unlike Snapdragon 615. Otherwise, the new SoCs are similar to Snapdragon 615, with the same Adreno 405 GPU. According to Qualcomm, devices using these chips will become commercially available in the second half of 2015.

• Kirin 620 (Hi6210) from HiSilicon (Huawei) is an octa-core Cortex-A53r0p3-based SoC running up to 1.2 GHz. The GPU is a Mali-450 MP4. Although performance (including single-core performance) is better than Snapdragon 410, it is not as optimized as chips such as MT6752 and runs at a relatively low clock speed. Multi-core performance scaling is less than expected.

Geekbench integer and memory scores comparison

The following table provides details about selected Geekbench integer and memory benchmark scores for different Cortex-A53-based SoCs, and also other smartphone SoCs from Qualcomm, MediaTek and Samsung for comparison.

                Arch    Max freq. JPEG C. IPC   JPEG C. Dijkstra      Stream Copy   Geekbench
                                  Single  x A7  Multi   Single Multi  Single Multi  Ref. number

Snapdragon 410  ARMv7     1.19      596   1.30   2384     810   2135   431   492    1551964
Snapdragon 615  AArch32 1.50/1.0    820   1.42   4979     886   3646   572   703    2015694
MT6732          AArch32   1.50      843   1.46   3357    1041   3002  1001  1199    1546611
MT6752          AArch32   1.69      952   1.46   7554    1144   4483  1071  1191    1583540
MT6795          AArch64   1.95     1026   1.37   8167     990   3802  1356  2068    2002894
MT6795T         AArch64   2.16     1128   1.36   8962    1064   4109  1350  2140    1984431
Hi6210          AArch32   1.20      660   1.43   3501     744   2772   602   900    1999304

Snapdragon 400  ARMv7     1.19      462   1.01   1860     700   2132   534   551    1938063
Snapdragon 801  ARMv7     2.46     1347   1.42   5437    1174   3586  1931  2144    1491681
Snapdragon 805  ARMv7     2.65     1475   1.45   4105    1230   4058  2117  2910    1502687
Snapdragon 810  AArch64  ?/1.55    1358          5972    1073   3584  1428  1838    2017257
MT6582          ARMv7     1.30      506   1.01   2027     748   2354   250   396    2017732
MT6592          ARMv7     1.66      643   1.01   5086     891   3327   261   388    2000008
MT6595          ARMv7   2.20/1.69  1350   1.59   6080    1844   5612  1652  1986    1591744
Exynos 5430     ARMv7   1.80/1.3   1056   1.52   5140    1102   3918  1457  1559    1556780
Exynos 5433     AArch32   1.89     1456   2.10   6209    1523   5728  1396  1458    2017193
Exynos 7420     AArch64  ?/1.50    1481          7168    1065   4596  1953  2579    2012972

The low performance of Snapdragon 410 is apparent in the scores, with normalized IPC (instructions per cycle to the equivalent of a 1.0 GHz Cortex-A7) for the CPU-speed sensitive single-core JPEG Compress benchmark being lower than that of other Cortex-A53-based SoCs, probably due to being limited to ARMv7. The Dijkstra benchmark even scores lower on Snapdragon 410 than on an equivalently clocked Snapdragon 400, and memory performance is also lower.

Snapdragon 615, while improving on Snapdragon 410, also appears to be less optimized than MT6732/MT6752 in terms of single-core IPC, despite a very similar clock frequency. Looking at multi-core performance, MT6752 is significantly faster than Snapdragon 615, largely due to being able run all eight cores at the maximum clock frequency. MT6732 and MT6752 also have significantly higher memory performance, reaching an impressive score for devices with a 32-bit memory interface.

The higher clock speed of MT6795 (Helio X10) brings benefits for integer performance, but due to the use of the AArch64 instruction set, normalized IPC is lower (1.36 vs 1.46 for JPEG Compress). This is especially true for the Dijkstra benchmark, where AArch64 mode imposes a significant penalty (this is also seen on other platforms utilizing AArch64).

Overall, a high-speed Cortex-A53 configuration such as implemented in the MT6795T comes fairly close to Snapdragon 801 for single-core performance, while being significantly faster for multi-core performance, at a significantly lower cost. Several metrics are also in the same ballpark as the current high-end leader Exynos 7420.

Analysis of the Geekbench Lua subtest

The Lua integer benchmark appears to be particularly sensitive to memory subsystem efficiency, including L2 cache size, and memory bandwidth as well being dependent on CPU speed. It is the kind of code that may frequently occur in actual practice on a smartphone.

                Arch      Lua     IPC   Lua    CPU    #CPUs
                          Single  x A7  Multi  Par.

Snapdragon 410  ARMv7      603    1.23  2137   3.54   4
Snapdragon 615  AArch32    709    1.15  1644   2.32   4 + 4
MT6732          AArch32    753    1.22  2419   3.21   4
MT6752          AArch32    842    1.21  2361   2.80   8
MT6795          AArch64   1053    1.31  8203   7.79   8
MT6795T         AArch64   1173    1.32  8847   7.54   8
Hi6210          AArch32    587    1.19  1740   2.96   8

Snapdragon 400  ARMv7      476    0.97  1874   3.94   4
Snapdragon 801  ARMv7      980    0.97  2880   2.94   4
Snapdragon 805  ARMv7     1016    0.93  2917   2.87   4
Snapdragon 810  AArch64   1283          1065   0.83   4 + 4
MT6582          ARMv7      514    0.96  1644   3.20   4
MT6592          ARMv7      651    0.95  1344   2.06   8
MT6595          ARMv7     1509    1.67  2498   1.66   4 + 4
Exynos 5430     ARMv7      981    1.33  1861   1.90   4 + 4
Exynos 5433     AArch32   1397    1.89  5478   3.92   4 + 4
Exynos 7420     AArch64   1409          7088   5.03   4 + 4

In this test, Snapdragon 410 performs reasonably well. MT6752's multi-core performance seems limited by a bottleneck, probably external memory bandwidth. MT6795's performance is impressive; while single-core performance falls a little short of Cortex-A57 based SoCs, for multi-core performance it blows past them, with CPU parallelism fully exploited. It seems the bottleneck present with the MT6752 (presumably memory bandwidth and the L2 cache memory size available to each core) is not present with the MT6795.

Qualcomm's Snapdragon 810 consistently scores in the 1000-1200 range for both the single-core and multi-core test, while the multi-core test would have been expected to be significantly higher. This appears to reflect a serious deficiency in the memory subsystem of the SoC (which might not only be related tot the LPDDR4 SDRAM controller, but also the on-chip L2 cache) which might also have negative implications for smoothness in every-day use.

Geekbench floating points subtests

Finally, let's look at floating point performance. The Mandelbrot subtest tests pure floating point performance, while the SGEMM and SFFT tests also significantly depend on memory performance.

                Arch      Mandelbrot                 SGEMM         SFFT
                          Single  IPC   Multi  Par.  Single Multi  Single Multi

Snapdragon 410  ARMv7      448    1.10  1794   4.00   245    489    317   1258
Snapdragon 615  AArch32    583    1.14  3611   6.19   303    688    426   2517
MT6732          AArch32    585    1.14  2336   3.99   337    653    430   1727
MT6752          AArch32    661    1.15  5257   7.95   384   1148    481   3870
MT6795          AArch64    823    1.24  6406   7.78   484   1542    618   4764
MT6795T         AArch64    912    1.24  7245   7.94   529   1659    694   5333
Hi6210          AArch32    467    1.14  3509   7.51   264    876    343   2178

Snapdragon 400  ARMv7      405    1.00  1620   4.00   203    634    285   1182
Snapdragon 801  ARMv7      788    0.94  3104   3.94   907   2816    992   3518
Snapdragon 805  ARMv7      848    0.94  3389   4.00  1011   2669   1130   4135
Snapdragon 810  AArch64   1100          5144   4.68   749   1828   1009   3643
MT6582          ARMv7      444    1.00  1765   3.98   230    512    328   1316
MT6592          ARMv7      568    1.00  4430   7.80   282    696    419   3397
MT6595          ARMv7     1284    1.71  5822   4.53   748   2337   1187   4255
Exynos 5430     ARMv7      990    1.61  4745   4.79   657   2491    896   3971
Exynos 5433     AArch32   1174    1.91  4883   4.16   751   2369   1044   4031
Exynos 7420     AArch64   1198          6129   5.12   945   2888   1313   4874

From these numbers its is clear that Cortex-A53 improves floating point performance somewhat when compared to Cortex-A7 at the same clock speed. When eight cores can run in parallel at high speed, multi-core floating point performance is impressive, as demonstrated by MT6752 and MT6795. Snapdragon 801 and 805 are looking a bit dated in this department.

In the memory-intensive SGEMM and SFFT tests, Snapdragon 400 comes close to Snapdragon 410, illustrating the lack of performance improvement by Snapdragon 410. In fact MediaTek's previous generation MT6582 matches the floating point performance of Snapdragon 410 across all tests.

The Cortex-A57 based SoCs have the highest single-core floating point performance, although the Cortex-A17-based MT6595 is also very strong. Exynos 5433 and Exynos 7420 beat Snapdragon 810 in most floating point tests, although the difference is not as large as it used to be with earlier results for Snapdragon 810.

Conclusion

It is clear that octa-core Cortex-A53-based SoCs can deliver strong performance at a relatively low cost, and this particularly true for MediaTek's new chips, MT6752 and MT6795. The MT6795, with its higher clock speed and dual-channel memory interface, can match current high-end chips in most metrics, being not much slower in single-core performance while being superior in multi-core.

One unknown question is whether the high maximum clock frequency of the MT6795 and MT6795T, which deliver impressive performance/dollar, translates to acceptable power consumption and battery life. Observations that power consumption for Cortex-A53 can quickly increase at higher frequencies for the Samsung-manufactured Exynos 5433 have been made, but MT6795 is manufactured on different process at TSMC and probably makes use of specific design optimizations for high clock speeds (ARM POP IP core hardening technology) that make power consumption more acceptable.

Sources: Geekbench Browser

Updated 10 March 2015.

Another symmetric octa-core CPU-based SoC announced (HiSilicon Kirin 620)

Huawei has just announced a new SoC, Kirin 620, with an octa-core Cortex-A53 CPU. The chip is the latest in a series of newly introduced octa-core Cortex-A53-based SoCs from companies such as MediaTek and Qualcomm as well as other players.

New Kirin 620 chip appears to target cost-sensitive segment

HiSilicon shows some smart design choices with this chip. It is clearly designed to be relatively cheap to manufacture (with a relatively limited chip die area) while still providing good performance for low/mid-range devices.

In the past, HiSilicon has been using CPU cores with a relatively large die area such Cortex-A9 and Cortex-A15, which do not result in a particularly cheap or power-efficient chip. However, the Cortex-A53 is the direct successor to the very power-efficient and extremely small Cortex-A7 core, which means even with eight cores the chip will still be relatively small as well as power-efficient.

The maximum CPU clock speed of 1.2 GHz is significantly lower than most other announced Cortex-A53-based SoCs, illustrating that the chip is intended for the cost-sensitive segment. Possibly, it is manufactured on TSMC's relatively economical 28LP process technology, which limits maximum performance.

Compared to MediaTek’s and Qualcomm’s new octa-core Cortex-A53-based chips, the Mali-450 MP4 GPU is notable because it does not support the OpenGL ES 3.0 API. However, OpenGL ES 2.0 is still the standard in the mobile market, and HiSilicon can probably improve cost and performance this way (especially since Mali-T62x and Mali-T760 are not cheap in terms of die size). Mali-T760 would have been faster and more power-efficient, but Mali-450 MP4 saves cost while still providing reasonable performance.

The new chip has several similarities with MediaTek’s MT6592, which is almost a year old, and has eight Cortex-A7 cores instead of Cortex-A53 and also a Mali-450 MP4 GPU.

Octa-core Cortex-A53 core CPU provides benefits for performance/Watt and performance/dollar

Because the Cortex-A53 (like its predecessor, the Cortex-A7) has a very small die size in comparison to higher-performance cores like Cortex-A57 and Cortex-A15, the use of eight cores instead of four does not very significantly raise the cost of the chip, while greatly increasing multi-core performance. Although not quite true for HiSilicon's chip due to the relatively low clock speed, several other Cortex-A53-based chips are also clocked at a relatively high frequency (in excess of 2 GHz for MT6795), resulting in respectable single-core performance as well, and making such a configuration suitable for the performance segment.

An octa-core configuration can provide real benefits in practice in a multi-threaded OS such as Android. Applications that can readily take advantage of eight cores include the Chrome browser and software video decoding and encoding libraries, all of which can improve the user experience. Because the eight cores are usually physically split into two clusters with a separate L2 cache, there is also room for further optimizations by the kernel scheduler in order to maximize performance and power efficiency.

For example, it might be possible for the scheduler to disable one of the two clusters of four CPU cores and its associated L2 cache during normal operation (when the load is not high), resulting in low power consumption. When more CPU power is needed, the second cluster comes online. Even when there are only a few threads, the scheduler might be able to detect the need for more L2 cache memory in a particular workload and move one or more threads to the second cluster. MediaTek's CorePilot technology, with which it has had experience since the MT6592, probably involves heuristics of this kind.

Overview of symmetric octa-core Cortex-A7 and Cortex-A53-based SoCs

The following table shows an overview of currently announced octa-core Cortex-A7 and Cortex-A53-based SoCs, starting with MediaTek's MT6592 which has been available for about a year.

(Click to enlarge)

Note that Qualcomm's Snapdragon 615 is not really a symmetric octa-core because it uses a pseudo-big.LITTLE configuration with four Cortex-A53 cores clocked higher and four cores clocked lower.

Performance comparison of octa-core Cortex-A7 and Cortex-A53-based SoCs

The following tables show CPU performance (using a representative Geekbench subtest result) as well GPU performance based on GFXBench for relevant SoCs and devices for which benchmark data is available. It includes both octa-core Cortex-A7 and Cortex-A53-based SoCs, as well as other existing SoCs from different market segments, for reference.

(Click to enlarge)

The first few columns of the table show a description of the SoC with CPU configuration, the name of a representative device model using the SoC and the maximum CPU clock speed. Then comes the Geekbench JPEG Compression benchmark test, both single-core and multi-core. This Geekbench subtest has been found to be relatively sensitive to CPU performance without being very sensitive to other factors such as L2 cache size.

The rightmost columns show information about the GPU. First listed are the GPU type and off-screen performance for the GFXBench T-Rex (OpenGL ES 2.0) and Manhattan (OpenGL ES 3.0) benchmarks. The offscreen tests always render into a 1920x1080 off-screen buffer, making results comparable between devices with different screen resolutions. The actual resolution used on the device comes next, followed by on-screen T-Rex benchmark benchmark performance and information relevant for battery life and long-term performance (which is affected by thermal throttling). This includes average long-term performance of the T-Rex on-screen benchmark, the battery size of the device and the battery life in minutes when running T-Rex on-screen long-term.

Mali-T760 appears to be highly efficient

Notable is that GPU performance of the MT6752 with Mali-T760 MP2 GPU as represented by the Lenovo A70-A entry in the GFXBench database is comparable with the Snapdragon 615-based HTC Desire 820, despite the latter's higher low-level pixel processing performance (such as evident in the ALU and Alpha Blending scores) provided by the Adreno 405 GPU.

This strongly suggests that ARM has made a big leap in terms of performance efficiency with the Mali-T760 GPU core in conjunction with compression-based bandwidth optimization technologies such as ARM Framebuffer Compression, Transaction Elimination and Smart Composition as well as good integration with the Cortex-A53 CPU architecture (which already shows memory performance improvements).

Based on GFXBench power efficiency data, none of the listed SoCs appears to be particularly power-efficient with a full GPU load with the complex T-Rex benchmark, but data for the Mali-T760 MP2-based MT6752 has yet to come in. However, the best battery life entries in the GFXBench database for the Samsung Galaxy Note 4 with Mali-T760 MP6-based Exynos 7 Octa shows the ability to run the on-screen T-Rex benchmark for more than 300 minutes with reasonable sustained performance on the very high resolution screen of the Note 4, which is compatible with relatively high power efficiency of the Mali-T760 GPU.

Note that power efficiency is likely to be better for typical GPU applications that are less demanding than GFXBench's T-Rex benchmark (this affects lower-end SoCs/GPUs more than higher-end ones).

Sources: CNXSoftware (Kirin 620 announcement), GFXBench results database, Geekbench browser

Updated December 25, 2014 (Correct memory interface information for Snapdragon 615).