Render output unit
The render output unit, often abbreviated as "ROP", and sometimes called (perhaps more properly) raster operations pipeline, is a hardware component in modern graphics processing units (GPUs) and one of the final steps in the rendering process of modern 3D accelerator boards. The pixel pipelines take pixel and texel information and process it, via specific matrix and vector operations, into a final pixel or depth value. This process is called rasterization. The ROPs perform the transactions between the relevant buffers in the local memory – this includes writing or reading values, as well as blending them together. Dedicated antialiasing hardware used to perform hardware-based antialiasing methods like MSAA is contained in ROPs.
Historically the number of ROPs, TMUs, and shader processing units have been equal. However, from 2004, several GPUs have decoupled these areas to allow optimum transistor allocation for application workload and available memory performance. As the trend continues, it is expected that graphics processors will continue to decouple the various parts of their architectures to enhance their adaptability to future graphics applications. This design also allows chip makers to build a modular line-up, where the top-end GPUs are essentially using the same logic as the low-end products.