Thursday, April 9, 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.

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