The ASUS Zenfone 2 (ZE551ML) Review: Game Changer

GPU Benchmarks

GFXBench Offscreen – T-Rex

The T-Rex test is based on OpenGL ES 2.0 and includes textures, material, geometry and particle effective that were highly detailed at the time of release. The graphics rendering engine features planar reflection, specular highlights and soft shadows, providing a good workout even for flagship smartphones and tablets. Offscreen tests are run at 1080p, regardless of the device’s native resolution, and are best used to compare the performance between competing silicon, not competing devices.

In this first test we see the Nexus 6 coming out on top with the OnePlus One not far behind, and it appears that the Adreno graphics in the Qualcomm chips outclasse the Zenfone 2's PowerVR G6430, with both ASUS phones at the bottom here – at least with OpenGL ES 2.0.

GFXBench Offscreen – Manhattan

Manhattan was the first benchmark to utilize OpenGL ES 3.0 features and uses a nighttime setting with a lot of external illumination to stress the GPU. It uses a deferred rending engine with multiple render targets for the geometry pass, includes both diffuse and specular lighting, uses depth shadow maps, bloom, depth of field and quite a bit more. 

With OpenGL ES 3.0 the Zenfone 2 has a better showing, with both models moving up a step. Samsung's Exynos chip (with Mali T760 graphics) is the winner this time with an impressive showing.

GFXBench Offscreen – ALU Performance

This test measures the pure shader compute performance using a fragment shader and rending a single full-screen quad.

An odd result here considering the OnePlus One only has a Snapdragon 801, but the Nexus 6 result was repeatable. Again the Zenfone results are lower than the Snapdragon devices, but this time it's the Galaxy Note 4 at the bottom.

GFXBench Offscreen – Alpha Blending Performance

Rendering semi-transparent quads with uncompressed textures allows this test to measure the alpha performance of the GPU directly.

Alpha performance with the Zenfone 2 was nearly identical between the two, and again we see these phones struggling to keep up with a result that is only half that of the Nexus 6.

GFXBench Offscreen – Driver Overhead

This test renders a large number of very simple objects one-by-one, changing state with each item in a pattern consistent with real-world applications. This allows the benchmark to measure the CPU overhead of the OpenGL driver.

Samsung's international Galaxy Note 4 seems well optimized for this driver overhead test, and the results aren't close.

GFXBench Offscreen – Fill Rate Performance

The portion of the test measures texture fill rate performance by rendering four layers of compressed textures, a very common scenario in gaming.

Back to a more real-world test we see raw performance of the Snapdragon 805's Adreno 420 graphics is too much for the rest of the phones tested.

GFXBench – Native Resolution

All of the above tests were run at 1080p to compare the performance of the GPU systems on equal ground. But smartphones are not equal ground as the displays that are part of the platform differ from unit to unit, and resolution can and does directly impact perceived GPU performance. Both the Nexus 6 and Glaxy Note 4 have 2560×1440 native resolution displays, while the Zenfone 2 and OnePlus One each have native 1920×1080 displays.

Here's were things start to get interesting. It's not surprising that the three phones with native 1080p panels would win this test against a pair of QHD (2560×1440) devices, but the Zenfone 2's showing is very impressive here in both tests.

3DMark

Use 3DMark Ice Storm Unlimited for chip-to-chip comparisons of the hardware inside your device without vertical sync, display resolution scaling and other operating system factors affecting the result. In Unlimited mode the rendering engine uses a fixed time step between frames and renders exactly the same frames in every run on every device. The frames are rendered in 720p resolution "offscreen" while the display is updated with small frame thumbnails every 100 frames to show progress.

Ice Storm Graphics test 1 stresses the hardware’s ability to process lots of vertices while keeping the pixel load relatively light. Hardware on this level may have dedicated capacity for separate vertex and pixel processing. Stressing both capacities individually reveals the hardware’s limitations in both aspects. Pixel load is kept low by excluding expensive post processing steps, and by not rendering particle effects.

Graphics test 2 stresses the hardware’s ability to process lots of pixels. It tests the ability to read textures, do per pixel computations and write to render targets. The additional pixel processing compared to Graphics test 1 comes from including particles and post processing effects such as bloom, streaks and motion blur. The numbers of vertices and triangles are considerably lower than in Graphics test 1 because shadows are not drawn and the processed geometry has a lower number of polygons.

The purpose of the Physics test is to benchmark the hardware’s ability to do gameplay physics simulations on CPU. The GPU load is kept as low as possible to ensure that only the CPU’s capabilities are stressed. The test has four simulated worlds. Each world has two soft bodies and two rigid bodies colliding with each other. One thread per available CPU core is used to run simulations. All physics are computed on the CPU with soft body vertex data updated to the GPU each frame. The background is drawn as a static image for the least possible GPU load. The Ice Storm Physics test uses the Bullet Open Source Physics Library.

The overall result with 3DMark is always going to scale with CPU speed as well as GPU horsepower, and here the difference in the two Zenfone SoCs is very clear. The graphics edge still goes to the faster phone, a sign that the 1.83 GHz clock speed might be a bottleneck with the 16GB version. The Nexus 6 enjoys another win here, showing the performance of the Adreno GPU yet again. Finally in the physics test the Zenfone 2 64GB wins out by more than 200 points, making the $500+ smartphones tested look rather slow in comparison. This Atom SoC can be very impressive.

Basemark X

Basemark X is the world’s most popular benchmarking tool for evaluation and cross-platform comparison of gaming and graphics performance between Android, iOS and Windows Phone 8 smartphone and tablets.

Basemark X is the only vendor-independent benchmark that utilizes the real-world game engine Unity which is very popular among game developers. This means that it scores correlate exceptionally well with real-life gaming performance.

Basemark X includes two game-like graphics tests: Dunes and Hangar. Both tests contain heavy graphics content rendered with detail and complexity, thus pushing the measured device to the limit. The polygon counts in test sequences are up to 911,000.

The Nexus 6 and Note 4 both finished ahead by a wide margin with both medium and high settings, and in this "real-life" gaming simulation both Zenfone models struggle in comparison (though the results are right there with the Snapdragon 801 powered OnePlus One with high settings).

Basemark OS II – Graphics

Basemark OS II is a system-level All-In-One benchmarking tool designed for measuring overall performance of smartphones and tablets from all platforms, including Android, iOS and Windows phone 8.

The benchmark features a comprehensive suite of tests including system, internal and external memory, graphics, web browsing, camera, battery and CPU consumption.

The final synthetic graphics benchmark brings us full-circle with another result that heavily favors the more expensive phones tested. In this case the Nexus 6 dominated, with both Snapdragon devices finishing well above the rest.