Many of the embedded/mobile GPUs are providing access to performance registers called Pixel Write Speed and Texel Write speed. Could you explain how those terms can be interpreted and defined from the actual GPU hardware point of view?
The performance registers/counters Pixel Write Speed and Texel Write speed maintain stats / count operations about pixel and texel processed/written. I will explain the peak (maximum possible) fill rates.
A picture element is a physical point in a raster image, smallest element of display device screen.
Pixel rate is the maximum amount of pixels the GPU could possibly write to the local memory in one second, measured in millions of pixels per second. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.
The pixel rate is calculated by multiplying the number of ROPs (Raster Operations Pipelines - aka Render Output Units) by the the core clock speed.
Render Output Units : The pixel pipelines take pixel and texel information and process it, via specific matrix and vector operations, into a final pixel or depth value. The ROPs perform the transactions between the relevant buffers in the local memory.
Importance : Higher the pixel rate, higher is the screen resolution of the GPU.
A texture element is the fundamental unit of texture space (a tile of 3D object surface).
Texel rate is the maximum number of texture map elements (texels) that can be processed per second. It is measured in millions of texels in one second
This is calculated by multiplying the total number of texture units by the core speed of the chip.
Texture Mapping Units : Textures need to be addressed and filtered. This job is done by TMUs that work in conjunction with pixel and vertex shader units. It is the TMU's job to apply texture operations to pixels.
Importance : Higher the texel rate, faster the game renders displays demanding games fluently.
Example : Not a nVidia fan but here are specs for GTX 680, (could not find much for embedded GPU)
Model Geforce GTX 680
Memory 2048 MB
Core Speed 1006 MHz
Shader Speed 1006 MHz
Memory Speed 1502 MHz (6008 MHz effective)
Unified Shaders 1536
Texture Mapping Units 128
Render Output Units 32
Bandwidth 192256 MB/sec
Texel Rate 128768 Mtexels/sec
Pixel Rate 32192 Mpixels/sec