PowerVR GX6450 vs PowerVR GXA6850

PowerVR GX6450

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The Imagination Technologies PowerVR GX6450 is a fast mobile graphics solution for smartphones and tablets, which can be found in ARM SoCs such as the Apple A8 (iPhone 6 and iPhone 6 Plus). The chip is available since Q3/2014 and of one of the fastest solutions in its class at the time of introduction.

Architecture and Performance

The GPU is based on the PowerVR Series 6XT (Rogue) Unified Shader architecture and integrates four clusters with two TMUs and 32 FP32-ALUs each. Therefore, the theoretical FP32 (full precision) compute performance per clock is identical to the previous G6430 (also 4 clusters) found in the Apple A7. Thanks to additional dedicated FP16-ALUs, however, the also important FP16 (half precision) performance has been greatly improved.

In the iPhone 6, the GPU should be clocked at around 450 MHz, delivering about 115 GLOPS (FP32). Compared to other mobile graphics solutions, the GX6450 outperforms the Qualcomm Adreno 330 (Snapdragon 800/801) and matches the more recent Adreno 420 (Snapdragon 805). Except for Nvidia's power hungry tablet chip Tegra K1 and its bigger cousin GX6650, the GX6450 is one of the fastest mobile GPUs in late 2014. Even the most advanced games and high resolution displays are handled without any problems. Among others, the GPU supports OpenGL 3.x/4.x, OpenGL ES 3.0 as well as DirectX 10.

Power Consumption

Thanks to the advanced 20-nanometer process and the relatively low clock rate, the GX6450 implementation in Apple's A8 offers a very high energy efficiency. On the other hand, the GPU has a comparatively "wide" architecture requirering a lot of transistors and die size (19 mm² in 20 nm).

PowerVR GXA6850

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The Imagination Technologies PowerVR GXA6850 is a fast mobile graphics solution (mainly) for tablets, which can be found in ARM SoCs such as the Apple A8X (iPad Air 2). The chip is available since Q3/2014 and of one of the fastest solutions in its class at the time of introduction.

Architecture and Performance

In contrast to previous speculations, the A8X integrates an 8-cluster PowerVR Series 6 (Rogue) GXA6850 consisting of two GX6450 GPUs (2x 4 clusters) instead of a single GX6650 (6 clusters). The name GXA6850 has been created by Anandtech, the design may also be called a GX6450MP2.

Each cluster offers four FP16 and two FP32 ALUs, leading to a compute power of about 230 GFLOPS FP32 at 450 MHz (clock rate estimated). The GXA6850 does not only beat the Qualcomm Adreno 420 (Snapdragon 805), but also the Nvidia Tegra K1 by a small margin. Thus, the GXA6850 is one of the fastest tablet GPUs as of 2014 and can handle even the most demanding mobile games in high resolutions. Among others, the GPU supports OpenGL 3.x/4.x, OpenGL ES 3.0 as well as DirectX 10.

Power Consumption

Thanks to the advanced 20-nanometer process and the relatively low clock rate, the GXA6850 implementation in Apple's A8X offers a very high energy efficiency. On the other hand, the GPU has a comparatively "wide" architecture requirering a lot of transistors and die size (about 38 mm² in 20 nm).

PowerVR GX6450PowerVR GXA6850
ManufacturerImaginationImagination
PowerVR Series 6XT (Rogue) Series
PowerVR GXA6850 256 @ 450 (?) MHz128 Bit
PowerVR GX6450 128 @ 450 (?) MHz64 Bit
PowerVR GX6250 (compare) 64 @ 700 (Boost) MHz64 Bit
PowerVR GXA6850 256 @ 450 (?) MHz128 Bit
PowerVR GX6450 128 @ 450 (?) MHz64 Bit
PowerVR GX6250 (compare) 64 @ 700 (Boost) MHz64 Bit
CodenameRogueRogue
ArchitecturePowerVR RoguePowerVR Rogue
128 - 256 -
Core450 (?) MHz450 (?) MHz
Bus64 Bit128 Bit
nono
DirectXDirectX 10DirectX 10
Technology20 nm20 nm
FeaturesOpenGL 3.x, 4.x, OpenGL ES 3.0OpenGL 3.x, 4.x, OpenGL ES 3.0
Introduced09.09.2014 09.09.2014
Manufacturerhttp://www.imgtec.com/powervr/series6xt....http://www.imgtec.com/powervr/series6xt....
CPUGPU Base SpeedGPU Boost / Turbo
Apple A82 x 1400 MHz? MHz? MHz

3DMark - Ice Storm Unlimited Graphics Score 1280x720 offscreen
min: 22509     avg: 23756.2     median: 23937 (5%)     max: 25254 Points
31542 Points (6%)
3DMark - Sling Shot OpenGL ES 3.0 Unlimited 2560x1440
2651 Points (20%)
3DMark - Sling Shot OpenGL ES 3.0 Unlimited Graphics 2560x1440
3474 Points (12%)
3DMark - Sling Shot Extreme (ES 3.1) Unlimited 2560x1440
2059 Points (30%)
3DMark - Sling Shot Extreme (ES 3.1) Unlimited Graphics 2560x1440
2377 Points (28%)
GFXBench (DX / GLBenchmark) 2.7
T-Rex HD Offscreen C24Z16 1920x1080 + PowerVR GX6450
T-Rex HD Offscreen C24Z16 1920x1080 + PowerVR GXA6850
T-Rex HD Onscreen C24Z16 + PowerVR GX6450
T-Rex HD Onscreen C24Z16 + PowerVR GXA6850
GFXBench 3.0 - Manhattan Offscreen OGL off screen
min: 17     avg: 19.1     median: 18 (3%)     max: 21 fps
min: 32     avg: 35     median: 35 (6%)     max: 37 fps
GFXBench 3.0 - Manhattan Onscreen OGL on screen
min: 15     avg: 23.7     median: 24 (7%)     max: 30 fps
min: 24     avg: 25.8     median: 25 (7%)     max: 27 fps
GFXBench - Aztec Ruins High Tier Onscreen
6.1 fps (4%)
GFXBench - Aztec Ruins High Tier Offscreen 2560x1440
5.3 fps (3%)
GFXBench - Aztec Ruins Normal Tier Onscreen
9.5 fps (5%)
GFXBench - Aztec Ruins Normal Tier Offscreen 1920x1080
14.2 fps (3%)
Basemark X 1.1 - High Quality
min: 15572     avg: 16055     median: 16055 (36%)     max: 16538 fps
29502 fps (67%)
Basemark X 1.1 - Medium Quality
41488 fps (92%)
PassMark PerformanceTest Mobile V1 - 2D Graphics Tests
min: 2320     avg: 2579.3     median: 2609 (12%)     max: 2809 Points
2956 Points (14%)
PassMark PerformanceTest Mobile V1 - 3D Graphics Tests
min: 1060     avg: 1678.7     median: 1984 (31%)     max: 1992 Points
1160 Points (18%)

Average Benchmarks PowerVR GX6450 → 100%

Average Benchmarks PowerVR GXA6850 → 115%

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* Smaller numbers mean a higher performance
1 This benchmark is not used for the average calculation

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Redaktion, 2017-09- 8 (Update: 2017-09-11)