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ASUS 3DP-V500TX
A. REGISTRY & DMA VARIABLES
A. REGISTR
Y
& DMA
DMA
V
ariables
GlintClockSpeed: This variable is used to indicate the oscillator frequency of the
reference board (this value cannot be read from the board). By default this value is
zero indicating that the clock frequency used should be the default for the chip revi-
sion. This variable should only be changed if the clock speed of the board is not the
default for the chip type.
This variable is read every time the Test button is used in the Display Applet (and
also at boot time). Thus to change the clock speed, start the Display Applet and
press the Test button. On return from the test screen the new clock speed will have
been loaded into GLINT. When asked if the test screen could be seen answer No
and press Cancel in the Applet. This will leave all system settings unmodified ex-
cept the GLINT clock speed will have been updated.
DMA Control Variables
GlintDMA.NumberOfBuffers: This defines the number of DMA buffers config-
ured for use by the 3D extension. As each 3D context is created a DMA buffer will
be allocated to it. Typically, each 3D application (whether OpenGL or another ac-
celerated 3D API) will use a single context. If all DMA buffers have been allocated
then shared memory buffers are used instead.
If this variable does not exist or its value is set to zero then use of DMA is disabled.
DMA will not be available if the installed GLINT board does not support DMA
transfers. In this case an event is logged in the system log file. This can be viewed
using the Event Viewer. The installation default is 4. You must reboot to change.
GlintDMA.SizeOfBuffer: This variable defines the size in bytes of each DMA
buffer. Its value will be rounded up to the next system page boundary. The size will
be limited to 256KB since this is the maximum size that can be specified to GLINT
for a DMA transfer. The installation default is 0x10000 (64KB). You must reboot
for changes in this variable to take effect.
GlintDMA.NumberOfSubBuffers: This variable describes the number of sec-
tions into which a single DMA buffer is divided for use by a 3D application. This is
used by interrupt driven DMA to construct a queue of buffers which are to be loaded
into GLINT by the DMA interrupt handler. The maximum size of the queue is
always 2 less than the number of sub-buffers specified. This is to allow the 3D
application to fill one buffer and GLINT to be performing DMA on another buffer.
The remainder can be queued.
Setting this variable to 2 disables interrupt driven DMA since not enough buffers are
available to create a DMA queue. DMA still works but the DMA buffer is split into
two parts so that GLINT can load one while the 3D application prepares the other.
Setting this variable to zero disables DMA and forces FIFOs to be used. This latter
feature is generally used only for comparing performance of DMA and non-DMA
operation (without needing a reboot).
