Glossary

The following is a collection and explanation of both PowerVR specific terms and general graphical terms.

ALU - Arithmetic Logic Unit. Responsible for processing shader instructions.

Early-Z - An umbrella term for a collection of optimisations commonly used by graphics cores. Early-Z techniques reduce overdraw by performing depth tests early in the graphics pipeline.

Firmware - A dedicated program running on the graphics core that handles hardware events.

For example: a tile processing operation completing.

Fragment - The data necessary to calculate a pixel colour. Multiple fragments may contribute to the colour of a pixel.

For example: when a transparent object is drawn in front of an opaque object.

Graphics pipeline - The sequence of processing stages within a graphics core that must be executed to render an image.

HSR - Hidden Surface Removal.

IMR - Immediate Mode Render.

ISP - Image Synthesis Processor.

Overdraw - The term “overdraw” refers to wastefully colouring pixels that do not contribute to the final image colour.

SIMD - Single Instruction, Multiple Data. Concurrent execution of a single instruction across multiple ALUs, where each ALU has unique input and output.

Scalar (shader architecture) - A shader architecture in which an ALU processes a single value at a time.

Pixel - The smallest addressable area of a frame buffer.

Rasterization - The process of determining which pixels a given primitive touches.

Render - The process of converting application-submitted data into coloured pixels that can be stored in the frame buffer.

Renderer - The tile processing stage of a TBDR pipeline. This includes rasterization and fragment shading.

TA - Tile Accelerator.

TBR - Tile Based Renderer.

TBDR - Tile Based Deferred Renderer.

Tile - A rectangular group of pixels. In TBR and TBDR architectures, the frame buffer is broken into many tiles. The tile size of each PowerVR graphics core is decided during hardware design, typically 32x32 pixels.

Tiler - The vertex shading, clipping, projection, culling, and tiling stages of a TBDR pipeline.

TSP - Texture and Shading Processor.

Vector (shader architecture) - A shader architecture in which an ALU processes multiple values simultaneously. Vector architectures commonly have a width of 4, allowing the ALU to calculate values for the ‘x’, ‘y’, ‘z’ and ‘w’ components of a vector data type.