From: Jon M. Taylor <taylorj@gaia.ecs.csus.edu>
  To  : ggi-develop@eskimo.com
  Date: Tue, 17 Aug 1999 16:00:37 -0700 (PDT)

Re: kgicon C&T

On Tue, 17 Aug 1999, Marcus Sundberg wrote:

> James Simmons wrote:
> > 
> > > >  Double buffering is not defined for fbdev :(
> > >
> > > But panning is, so ask for: yres_virtual == 2*yres when calling
> > > FBIOPUT_VSCREENINFO, and use FBIOPAN_DISPLAY to flip between the
> > > top half and the bottom half.  Right James ?
> > 
> > Yes you can do that. What I was talking about where cards that do have a
> > seperate buffer for double buffering.
> 
> Never heard of such hardware. Any examples?

	Most new hardware supports explicit double/triple buffering, as
opposed to the SetOrigin()-based SVGA-style double buffering.  The
differences are minimal, and mostly involve the hardware taking care of
automating buffer flips on vsync.  The back buffer is still just another
chunk of video memory, it just doesn't have to be physically continguous
with the primary framebuffer anymore.  This doesn't matter, though - as
long as the front and back buffers are page-aligned in size and accessible
through PCI/AGP-style memory mapping, VM trickery can be used to map the
back buffer region to the end of the front buffer region for fbdev when
necessary.

Jon


---
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