Samsung S5PC100, User Manual

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S5PC100 USER’S MANUAL (REV1.0) 3D-ACCELERATOR
9.6-29
3.8 VERTEX CACHE CONTROL
The EnVC and NumOutAttrib fields in HI_CONTROL controls the way how the vertex cache works. If EnVC field
is 0, then the vertex cache is disabled. The NumOutAttrib field stores the number of output attributes from the
vertex shader. The number of output attributes determined by NumOutAttrib field is transferred to the primitive
engine.
Note that when HI_CONTROL is wrtten by CPU, the Post Vertex Cache is cleared (or initialized) automatically.
When you send a series of indices for a geometry data, you send another different geometry. In this case, the
index for the previous geometry data which is remained in Vertex Cache can be hit when the index of the new
geometry data is sent. Hence, when you send multiple geometry data using index mode, you must clear the
content of Vertex Cache between geometries. Vertex Cache is cleared automatically when HI_CONTROL is
written by CPU. Although the HI_CONTROL value is not changed, HI_CONTROL can be rewritten with the same
value to clear the contents of Vertex Cache.