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TVP4020
Programmers Reference Manual
Programming Tips
141
that it can be downloaded. See section §5.8.2 to §5.8.6 for further
details.
7.1.7
AGP Support
The Advanced Graphics Port extensions to the PCI protocol are
supported by TVP4020. When in an AGP slot, TVP4020 will function as
a 66MHz PCI device, and also perform single edge AGP read master
transfers, optionally with sideband addressing.
7.2
Graphics Hyperpipeline
7.2.1
Disable Unused Units
Any unit which is not being used should be disabled. This will maximize
pixel throughput in the graphics core.
It is important to make sure that data is not being read from the texture
buffer, localbuffer or framebuffer unless it is needed. For instance it is
perfectly possible to set-up the localbuffer read unit such that P
ERMEDIA
reads per pixel information, such as Z or stencil buffer data, which is
then discarded. The effect will be the same visually, but the cost in
performance of making the memory accesses will be very high. It is also
important to set the LBDisableUpdate bit in the Window register if
localbuffer writes are not needed.
For optimal performance, hardware writemasks should be used in
preference to software masks.
7.2.2
Avoid Unnecessary Register Updates
P
ERMEDIA
control registers maintain their state between primitives so they
do not need to be updated unless the data needs to change. For
example, the dY register might be set to +1 for a trapezoid and does not
need to be reloaded until a line primitive is drawn.
All delta values and start values are maintained across primitives, so if
two triangles share a dominant edge, the start and dominant edge
values do not need to be calculated or loaded twice.
Similarly, window clipping need not reload all the registers for each clip
rectangle. For example: Load the registers ready for a primitive to be
drawn, then enter a loop which repeatedly loads the coordinates for a
clip rectangle into the Scissor unit and then sends the Render command.
Any number of clip rectangles can be processed in this way but
P
ERMEDIA
requires only one set-up for each primitive.
Summary of Contents for TVP4020 PERMEDIA 2
Page 1: ...Texas Instruments TVP4020 PERMEDIA 2 Programmer s Reference Manual Issue 4 ...
Page 284: ...TVP4020 Programmers Reference Manual A Gouraud Shaded Triangle 275 ...
Page 292: ...TVP4020 Programmers Reference Manual Register Tables 283 ...
Page 314: ...TVP4020 Programmers Reference Manual Index 305 ...
Page 315: ...Index TVP4020 Programmers Reference Manual 306 Index ...
Page 323: ...Index TVP4020 Programmers Reference Manual 314 ...