Product specifications

VT8601A Apollo PLE133
Revision 1.82 October 22, 2001 -113 3D Graphics Engine Registers
Technologies, Inc.
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GEbase + 20 – Graphics Engine Status............................ RO
Writing to this register resets the GE.
31 Bresenham Engine Status
0 Idle
1 Busy
30 Setup Engine Status
0 Idle
1 Busy
29 SP / DPE Status
0 Idle
1 Busy
28 Memory Interface Status
0 Idle
1 Busy (access for screen refresh doesn’t count)
27 Command List Processing Status
0 Idle
1 Busy
26 Block Write Status
0 Idle
1 Busy
25 Command Buffer Status
0 Not full
1 Full
24 Reserved .........................................always reads 0
23 PCI Write Buffer Status
0 Empty
1 Not empty
22 Z Check Status
0 Engine busy: All Z tests performed so far
have failed in the command being executed.
Engine idle: All Z tests performed in the last
command have failed.
1 Otherwise
Logically, this bit is the OR of all Z test results
performed in the latest command
21 Effective Status
0 Current display base register is not yet
effective (the frame is not displayed)
1 It is effective
20 Left View Status
0 Current display base register is not yet
effective (the frame is not displayed)
1 It is effective
19 Last View Displayed / Being Displayed
0 Right View
1 Left View
18-11 Reserved .........................................always reads 0
10-0 Scan Line Currently Being Displayed
There are two input FIFOs to buffer data and commands from
the host, the Command FIFO (8 levels deep) and the
Bresenham FIFO (2 levels deep). Drawing commands,
Drawing Environment, and Frame Buffer Control are routed
through the Command FIFO. Primitive Type and Geometry
Primitives are routed through the Bresenham FIFO.
Commands in the Command FIFO don’t take effect until a
prior command is executed or the task in progress is finished.
Parameters in the Bresenham FIFO don’t take effect until a
prior parameter is phased out (reaches the end of an edge).