xserver on OpenGL

[Allen Akin]

(I forgot to followup on this point...)

On Mon, Dec 08, 2003 at 09:46:29AM -0800, Keith Packard wrote:
| I would have thought that the memory allocation problem was already solved 
| though; pbuffers look a lot like textures to me.

At the conceptual level, textures have more structure -- mipmaps and
cubemaps in particular.  Available texel formats may also differ from
pixel formats.  Superbuffers generalize this a bit.

At the hardware level, the access patterns for textures are very
different from those of pbuffers.  In some designs they have to be
stored in different formats (e.g. tiled rather than linear) or even in
physically separate memories.  Nowadays the popular solution is to
budget a lot of transistors for texture cache and extra wires for
parallel memory accesses.  But it's still true that textures tend to be
written infrequently and read frequently, while PBuffers are written
frequently, so allocation and caching of the two may differ.

Allen