iOS Hardware Guide
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iOS Hardware Guide

Hardware models

Following table summarizes iOS hardware available in devices of various generations:

Common to all iOS devices

Original iPhone

iPhone 3G

iPhone 3GS

iPhone 4

iPod Touch 1st generation

iPod Touch 2nd generation

iPad

Graphics Processing Unit and Hidden Surface Removal

The iPhone/iPad graphics processing unit (GPU) is a Tile-Based Deferred Renderer. In contrast with most GPUs in desktop computers, the iPhone/iPad GPU focuses on minimizing the processing required to render an image as early in the processing of a scene as possible, so that only the pixels that actually will be seen consume processing resources.

The GPU's frame buffer is divided up into tiles and rendering happens tile by tile. First, triangles for the whole frame are gathered and assigned to the tiles. Next, visible fragments of each triangle are chosen. Finally, the selected triangle fragments are passed to rasterizer (triangle fragments occluded from the camera are rejected at this stage).

In other words iPhone/iPad GPU implements Hidden Surface Removal operation at reduced cost. Such architecture consumes less memory bandwidth, has lower power consumption, and utilizes texture cache better. Tile-Based Deferred Rendering allows the device to reject occluded fragments before actual rasterization which is effective to keep overdraw low.

For more information see also:

SGX series

Starting from iPhone 3GS and newer devices are equipped with SGX series of GPUs. SGX series features support for OpenGL ES2.0 rendering API, vertex and pixel shaders. Fixed-function pipeline is not supported natively on such GPUs, instead it is emulated by generating vertex and pixel shaders with analogous functionality on the fly.

SGX series fully supports MultiSample anti-aliasing.

MBX series

Older devices such as iPhone, iPhone 3G, iPod Touch 1st and 2nd Generation are equipped with MBX series of GPUs. MBX series supports only OpenGL ES1.1, fixed function Transform&Lighting pipeline and 2 textures per fragment.

Texture Compression

The only texture compression format supported by iOS is PVRTC. PVRTC provides support for RGB and RGBA (color information + alpha channel) texture formats and can compress single pixel to 4 or 2 bits.

PVRTC format is essential to save memory footprint and to reduce consumption of memory bandwidth (rate at which data can be read from memory, usually very limited on Mobile devices).

Vertex Processing Unit

The iPhone/iPad has a dedicated unit responsible for vertex processing. It runs calculations in parallel with rasterization. In order to achieve better parallelization, the iPhone/iPad processes vertices one frame ahead of the rasterizer.

Unified Memory Architecture

Both CPU and GPU on the iPhone/iPad share the same memory. The advantage is that you don't need to worry about running out of video memory for your textures (unless, of course, you run out of main memory too). The disadvantage is that you share same memory bandwidth for gameplay and graphics. The more memory bandwidth you dedicate to graphics, less you will have for gameplay and physics.

Multimedia CoProcessing Unit

The iPhone/iPad main CPU is equipped with a powerful SIMD (Single Instruction, Multiple Data) coprocessor either supporting VFP or NEON architectures. The Unity iOS run-time takes advantage of these units for multiple tasks such as calculating skinned mesh transformations, geometry batching, audio processing and other calculation-intensive operations.

Page last updated: 2011-02-28