Tuesday, March 10, 2015

Qualcomm's Snapdragon 808 fixes flaws of Snapdragon 810

Snapdragon 808 (MSM8992) is a performance-oriented SoC that Qualcomm announced last year together with Snapdragon 810. It has similarities to Snapdragon 810 (MSM8994), including the use of ARM Cortex-A57 CPU cores and Cortex-A53 cores in a big.LITTLE configuration. Snapdragon 808 appears to fix some of the performance flaws that are apparent in Snapdragon 810, especially the memory subsystem, while being significantly less costly.

Snapdragon 808 features

Features and differences with Snapdragon 810 include:

  • Snapdragon 808 has only two Cortex-A57 cores (revision r1p2) compared to four Cortex-A57 cores (revision rp1p1) for Snapdragon 810. Both contain four Cortex-A53 cores.
  • Snapdagon 808 has a more economical dual-channel LPDDR3 memory interface, compared to the LPDDR4 interface of Snapdragon 810.
  • Snapdragon 808 has an Adreno 418 GPU, compared to Adreno 420 in Snapdragon 810, presumably with somewhat lower performance.
  • Manufactured on TSMC's 20 nm process, the same as Snapdragon 810.
  • 4K resolution video playback (H.264/H.265), on-device display resolution up to 2560x1600 (Snapdragon 810 theoretically supports 4K on-device display resolution, but all currently announced smartphones using Snapdragon 810 are limited to a resolution of 1920x1080).


Early benchmark results suggest Snapdragon 808 fixes performance flaws of Snapdragon 810

Early benchmarks for Snapdragon 808 have already appeared on the Geekbench Browser. We can compare Snapdragon 808's single-core performance with Snapdragon 810 and Exynos 7420, all of which run in AArch64 mode in the published benchmark results.

To reduce the impact of thermal throttling, the best Geekbench subtest results for a given device have been collected and combined in the table below. I have made an attempt to estimate the actual maximum clock speed of the Cortex-A57 cores during the benchmarks, partly based on the maximum frequency reported by Geekbench when it appears to apply to the "big" cores and not the "LITTLE" cores.

SoC          "big" CPU                    Arch     JPEG (int)  Lua (int)   Mandelb. (float)
                                                   Comp. IPC         IPC         IPC

MSM8992      2 x 1.69? GHz Cortex-A57r1p2 AArch64  1257  1.96  1385  1.99  1031  1.79
MSM8994      4 x 1.8? GHz Cortex-A57r1p1  AArch64  1358  1.96  1283  1.73  1100  1.79
Exynos 7420  4 x 1.97 GHz Cortex-A57r1p0  AArch64  1486  1.96  1409  1.74  1198  1.78

MT6795       8 x 1.95 GHz Cortex-A53r0p2  AArch64  1026  1.37  1053  1.31   823  1.24
MT6795T      8 x 2.16 GHz Cortex-A53r0p2  AArch64  1128  1.36  1173  1.32   912  1.24

The IPC figures are calibrated on the Cortex-A7 core, whose IPC is fixed at 1.00. Fixing the maximum cock speed to 1.8 GHz for the MSM8994 (Snapdragon 810) results (based on HTC One M9 entries) and at 1.69 GHz for the MSM8992 (Snapdragon 808) produces similar IPC figures for the JPEG Compress integer test and the Mandelbrot floating point test, making them reasonably plausible. The best Lua subtest result for the MSM8992 shows a higher IPC, which may reflect improved L2 cache performance in the MSM8992, which uses a later revision of the Cortex-A57 core.

The single-core CPU performance results show no suprises, with Snapdragon 808 showing good performance that is slightly lower than Snapdragon 810, proportional to the lower maximum clock frequency in the tested devices. However, the Lua test shows higher performance with Snapdragon 808, which is especially true for the multi-core test (results not shown), where Snapdragon 810 seems to be limited to a score of about 1200 with little gain when compared to single-core performance, while Snapdragon 808 consistently scores in the region of 4000.

Memory subsystem performs much better than Snapdragon 810

The following table lists Geekbench scores for some memory-dependent tests. 

SoC          "big" CPU                    Arch     Stream Copy  SGEMM SFFT  SGEMM SFFT
                                                   Single Multi             Multi Multi
MSM8992      2 x 1.69? GHz Cortex-A57r1p2 AArch64  1527   1733   767  1126  1678  2946
MSM8994      4 x 1.8? GHz Cortex-A57r1p1  AArch64  1428   1838   741  1009  1870  3649
Exynos 7420  4 x 1.97 GHz Cortex-A57r1p0  AArch64  2003   2622   957  1363  2888  5014

MT6795       8 x 1.95 GHz Cortex-A53r0p2  AArch64  1356   2068   484   618  1542  4764
MT6795T      8 x 2.16 GHz Cortex-A53r0p2  AArch64  1350   2140   529   694  1659  5333

Notably, Snapdragon 808 delivers memory performance similar to Snapdragon 810 at much lower cost, despite using only a regular LPDDR3 memory interface, as compared to the Snapdragon 810's LPDDR4 memory interface which in theory delivers almost twice the bandwidth. This provides clear evidence that the Snapdragon 810's memory interface is still flawed, while that of Snapdragon 808 is much more optimized. Snapdragon 808 even beats Snapdragon 810 in the single-core SGEMM and SFFT test, despite running at a lower clock speed, which probably also reflects a more optimized and functional memory controller. Even in the multi-core SGEMM and SFFT tests, Snapdragon 808 is not much behind Snapdragon 810 despite having only half the number of CPU cores.

Comparison with MT6795

In the marketplace, Snapdragon 808 may compete with MediaTek's MT6795 (Helios X10), which is a cost-effective performance-segment SoC that only uses Cortex-A53 cores. Comparing Geekbench subtest results, MT6795 scores signficantly lower than Cortex-A57-based SoCs such as Snapdragon 808 in single-core benchmarks, although the gap is not very large except in the SFFT benchmark. The MT6795 does relatively well in multi-core benchmarks, where it beats the Cortex-A57-based Snapdragon 808 and Snapdragon 810 in most cases by a considerable margin, especially in the JPEG Compress, Lua and Mandelbrot tests which are sensitive to the number of CPU cores (multi-core scores have not been listed for these tests in the tables above). As an example, MT6795 scores 8167 in the multi-core JPEG Compress test, twice the score of Snapdragon 808 and almost 40% higher than Snapdragon 810.


Snapdragon 808 appears to be a much more optimized, less flawed SoC product than Snapdragon 810 that may perform similarly or even better than Snapdragon 810 in practical use cases due to the performance flaws present in Snapdragon 810. At the same time, Snapdragon 808 is likely be considerably cheaper. The only caveat is the question of whether excessive heat production makes thermal throttling necessary to the same degree as Snapdragon 810. With only two Cortex-A57 cores, the SoC should be less problematic in this regard.

Source: Geekbench Browser (MSM8992 results), Geekbench Browser (MSM8994 results), Qualcomm (MSM8992 specifications)

Updated 15 March 2015.

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