GPU Performance: Tegra 2
As we’ve mentioned in the past, mobile devices like smartphones and tablets use what’s known as a system-on-chip (SoC). This integrates the processor, GPU, RAM, and several other subsystems onto single device. Since all of those components sit next to each other on the same chip, there is greater efficiency in data transfers, while reducing the amount of space consumed on the PCB.
| SoC | Apple A4 (iPad) | Apple A5 | Nvidia Tegra 2 |
|---|---|---|---|
| Tablets | Apple iPad | Apple iPad 2 | Acer Iconia Tab A500Asus Eee Pad TransformerMotorola XoomSamsung Galaxy Tab 10.1 |
| Processor | 1 GHz ARM Cortex-A8 (single-core) | 1 GHz ARM Cortex-A9 (dual-core) | 1 GHz ARM Cortex-A9 (dual-core) |
| Memory | 256 MB 333 MHz LP-DDR (single-channel) | 512 MB 1066 MHz LP-DDR2 (dual-channel) | 1 GB 667 MHz LP-DDR2 (single-channel) |
| Graphics | PowerVR SGX535 (single-core) | PowerVR SGX545MP2 (dual-core) | ULP GeForce (single-core) |
| L1 Cache(Instruction/Data) | 32 KB / 32 KB | 32 KB / 32 KB | 32 KB / 32 KB |
| L2 Cache | 640 KB | 1 MB | 1 MB |
Tegra is Nvidia’s SoC brand, and it symbolizes the company’s effort to tap into the mobile market beyond its desktop-derived GeForce graphics processors. For those unfamiliar with Tegra 2, read page eight of our Motorola Xoom review for a full discussion GPU architecture. On the CPU side, Tegra 2 shares the same dual-core Cortex-A9, which offers a substantial boost from Cortex-A8 used in the first-generation iPad. Read Apple's iPad 2 Review: Tom's Goes Down The Tablet Rabbit Hole for a full discussion of Cortex-A9 performance.
While we've already covered Tegra 2, it's important to examine the graphics performance of each tablet. Sy Choudhury, director of product management at Qualcomm, once stated, "There is a misconception that the same processor and operating system gives the same performance." That's a phenomenon found on every tablet and smartphone. Why is it wrong to expect the same performance from all Honeycomb-based Tegra 2 tablets? Hardware vendors get access to the same optimizations from the SoC developer, but not all of the software-based tweaks are enabled by OEMs.
| GPU (System-on-Chip) | PowerVR SGX 535 (Apple A4) | PowerVR SGX 543 (Apple A5) | ULP GeForce (Tegra 2) |
|---|---|---|---|
| SIMD | USSE | USSE2 | Core |
| Pipelines | 2 (unified) | 4 (unified) | 8 (4 pixel / 4 vertex) |
| TMUs | 2 | 2 | 2 |
| Bus Width (bit) | 64 | 64 | 32 |
| Triangle rate @ 200 MHz | 14 MTriangles/s | 35 MTriangles/s | ? |
The ULP GeForce has a maximum operating frequency of 300 MHz, but device vendors can tweak this setting to save on power. Nvidia provides less information on the Tegra 2 than it does for its desktop GPUs, so it’s best to move on to benchmarks. As in our iPad 2 review, we're turning to GLBenchmark 2.0.
In terms of frames rendered in a set period, the Galaxy Tab 10.1 performs as well as other Android-based tablets running Honeycomb 3.1. Interestingly, the TouchWiz UI update enables graphics performance closer to the Eee Pad Transformer with Honeycomb 3.2. This implies one of two possibilities.
- Samsung could be enabling performance enhancements in the UI update.
- The TouchWiz UI is less resource-intensive than Honeycomb 3.1.
Whatever the reason, the Galaxy Tab 10.1 leads the pack as the best-performing Tegra 2-based tablet.
If you want to go into more depth than what is provided here, the full results of GLBenchmark 2.0 have been posted on Google Docs.