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<A HREF="P9000.html"><EM>XFree86 P9000 Server Release Notes</EM></A>
 <b>:</b> <EM>XFree86-DGA Extension Support </EM><BR>
<b>Previous:</b> <A HREF="P90005.html"><EM>Acceleration </EM></A><BR>
<b>Next:</b> <A HREF="P90007.html"><EM>High Color and TrueColor </EM></A>


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  <H2><A NAME="8"></A>6. XFree86-DGA Extension Support </H2>

<p>The XFree86-DGA extension is now supported.  Note that
XF86DGASetViewPort command is not fully implemented due to hardware
limitations of the P9000.  The SetViewPort and SetVidPage commands
have been hacked to allow double buffering under certain conditions. </p>

<p>For cards with 1MB or modes where xres*yres*Bpp &gt; 1024K,
no double buffering is supported.  In this case, the bank size
returned is equal to the amount of video memory.  Using
the XF86DGASetViewPort and XF86DGASetVidPage commands have
no results. </p>

<p>For cards with 2MB and for modes where virtualX*virtualY*Bpp &lt; 1024K,
the behaviors of SetViewPort and SetVidPage are modified to allow
double buffering.  The bank size returned by XF86DGAGetVideo is
equal to xres*yres*Bpp.  In this mode, there are two buffers
which can be written to, read from, and displayed.  The
XF86DGASetVidPage command can be used to switch between
buffers 0 and 1 for I/O.  Whichever buffer is selected will
be available through the linear aperture with no offset.
If XF86DGASetViewPort is called with ypos &lt; yres, it 
will cause buffer 0 to be displayed.  If ypos &gt;= yres,
buffer 1 will be displayed.  The result of this behavior
is that programs which switch banks as necessary
and which use two vertically adjacent banks should
work with no P9000-specific changes. </p>


 <HR NOSHADE>
<A HREF="P9000.html"><EM>XFree86 P9000 Server Release Notes</EM></A>
 <b>:</b> <EM>XFree86-DGA Extension Support </EM><BR>
<b>Previous:</b> <A HREF="P90005.html"><EM>Acceleration </EM></A><BR>
<b>Next:</b> <A HREF="P90007.html"><EM>High Color and TrueColor </EM></A>



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