pixel (depending upon whether the MultiBuffer(tm) option is installed).  This high
capacity allows storage of color, depth, texture, and numerous other special-purpose
data fields to Support advanced rendering features.


3.1.2 PC Boards
 

Using the latest 10-layer, fine-line printed circuit board (PCB) technology, the
PowerVision graphics subsystem consists of four triple-high EUROcard boards (five if
MultiMuffer option installed) with up to 500 16-pin IC equivalents per board.  The
ability to pack components densely on these PCBs reduces the cost of providing the
latest generation 3D graphics architecture.
 
3.1.3 Geometry Subsystem
 
The Geometry Subsystem is connected to the parallel processing CPU subsystem via
the proprietary 64-bit Power Series Bus interface.  This subsystem receives world
coordinate geometric data over the Power Series Bus, performs specified
transformations and lighting computations, and sends the screen space data to the
Scan Conversion Subsystem.  The major components of the Geometry Subsvstem are
the Command Processor and the SIMD-organized Geometry Engine.


3.1.4 Command Processor
 

The PowerVision Command Processor (CP) receives command tokens and data from
the Power Series Bus and distributes command packets to the four Geometry Engine
modules.  The CP accepts coordinate data from the RISC host in four formats: 16-bit
integer, 24-bit integer, 32-bit IEEE floating point, and 64-bit IEEE double-precision
floating point.  Color data are also accepted in packed byte format.

The Command Processor converts all incoming data words to a uniform floating
point format. regardless of the input representation.  In addition, for each 3D vertex
specified, the CP fills in any parameters not supplied by the user, from a repository of
current values specified earlier, and outputs a complete packet of parameters.  An
input FIFO buffers data from the host, eliminating unnecessary protocol overhead.