Thursday, May 21, 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.


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