[ILUG] hardware accel - radeon 9000

[Dermot McGahon]

On Fri, 21 May 2004 12:03:09 +0100, Conall O'Brien <conall at conall.net>  
wrote:

> Perhaps someone more familiar with tech specs of monitors can tell us
> what it really does.

http://www.tldp.org/HOWTO/Framebuffer-HOWTO-3.html

"A framebuffer device is an abstraction for the graphic hardware. It  
represents the frame buffer of
  some video hardware, and allows application software to access the  
graphic hardware through a
  well-defined interface, so that the software doesn't need to know  
anything about the low-level
  interface stuff [Taken from Geert Uytterhoeven's framebuffer.txt in the  
linux kernel sources]"

Basically, a framebuffer is a software abstraction of the video memory
of your graphics card. All video cards pretty much follow the VESA specs
to implement standard ways to interact with them, hence the ability to
use a vesafb with any card. Other framebuffer drivers specific to the
different card families have been written to abstract away specific
details of the h/w. These are implemented as kernel modules.

X has a long history and does things a little differently. Before there
was all this kernel code specific to different graphics adaptors, X had
to implement this abstraction layer in user space with some kernel
support, but limited.

DRI/DRM is yet another hunk of software that lets applications talk
to video cards, in this case allowing use of modern GPU co-processor
capabilities.

So, you've a choice, use framebuffers (embedded systems), use framebuffer
while booting then change over to X (standard desktop), use framebuffer
while booting then change over to X/DRI/DRM (games, 3D acceleration etc)

It's amazing, apart from the great efforts of DRI/DRM how *little* of
the capabilities of the latest graphics cards are being used by linux
graphics layers. Windows is much better in this regard because the
working relationship between MS and the video card manufacturers is
good.

At the moment they are basically ignoring requests from open source
developers for specs, which is not nice, but they're perfectly
entitled to do so. It wasn't always like that though, specs used to
be much more available and it's likely specs will become available
again. Video card industry is undergoing a huge growth spurt at the
moment. Things will settle down and then maybe we'll get some specs
again. We live in hope.


Dermot.
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