3D GPU fill rate performance with GC7000lite

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3D GPU fill rate performance with GC7000lite

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cphealy1
Senior Contributor I

According to the i.MX8M reference manual, the GC7000lite at 800Mhz is capable of 1.6 Giga pixel/sec fill rate.  We need to better understand this number.  My assumption is that this means the GPU can do 2 pixels/clock cycle due to there being 2 texture units and 2 pixel units in the GPU just like with the i.MX6q(p).

Typically, the GPU will have different pixel fill rates depending on the type of operation being performed.  For example, with some GPUs, you get the highest fill rate ONLY when filling with a solid color and not from a texture.  Then you get some lower fill rate when filling with texture data sampled from an RGB buffer, and lastly you get an even lower fill rate when filling pixels that are sampled from various YUV texture buffers.  We are looking for documentation that explains what the fill rate is for each type of pixel being filled.  Preferably, some charts like the charts that are available in the i.MX6q reference manual that describe the number of pixels/clock for each of the different operations the 2D GPU supports.  Below is an example of what we are looking for with the GC7000lite GPU:  (This example data is from the Vivante GC320 in the i.MX6q.)

fill_rate.png

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Bio_TICFSL
NXP TechSupport
NXP TechSupport

Hi Chris,

GPU documentation does not provide such information unfortunately. The fill rate provided in documentation shows how fast a color is rendered on screen but does not take into account the sampling of a texture or any other operation.
Sampling a RGB texture and render it will lower the fill rate indeed. Sampling a YUV texture will not necessarily take more time than a RGB texture, because YUV formats often have lower bit depth than RGB formats.

Regards

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cphealy1
Senior Contributor I

We require the exact details for the different theoretical GPU rendering use cases.  Vivante must have the necessary documentation to answer this question.

Specifically we need answers for rendering to both RGB565 and ARGB8888/ABGR8888 destination formats when the source formats are ARGB8888/ABGR8888, XRGB8888/XBGR8888, and YUY2/UYVY. 

Additionally, we need to understand what the fast clear fill rate is under various buffer depth configurations.

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Bio_TICFSL
NXP TechSupport
NXP TechSupport

Hi Chris,

In the Vivante doc, there is no details on performance obtained according to these different formats.
The only information we have regarding fill rate is that gpu can generate 2 texels or 2 pixels per cycle. So we can only deduce that it should take around twice the time to render from a texture than rendering a solid color.

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