Editing Direct Rendering Infrastructure (section)

== DRI1 ==
In the original DRI architecture, due to the memory size of [[video card]]s at that time, there was a single instance of the screen [[front buffer]] and [[back buffer]] (also of the ancillary [[depth buffer]] and [[stencil buffer]]), shared by all the DRI clients and the X Server.<ref name="Packard 2008" /><ref name="Packard 2009" /> All of them rendered directly onto the back buffer, that was [[Page flipping|swapped]] with the front buffer at [[vertical blanking interval]] time.<ref name="Packard 2008" /> In order to render to the back buffer, a DRI process should ensure that the rendering was [[Clipping (computer graphics)|clipped]] to the area reserved for its [[Window (computing)|window]].<ref name="Packard 2008" /><ref name="Packard 2009" />

The [[Synchronization (computer science)|synchronization]] with the X Server was done through [[Unix signal|signals]] and a [[shared memory]] buffer called the SAREA.<ref name="Packard 2009" /> The access to the DRM device was exclusive, so any DRI client had to [[Lock (computer science)|lock]] it at the beginning of a [[Rendering (computer graphics)|rendering]] operation. Other users of the device &mdash;including the X Server&mdash; were blocked in the meantime, and they had to wait until the lock was released at the end of the current rendering operation, even if it wouldn't be any conflict between both operations.<ref name="Packard 2009" /> Another drawback was that operations didn't retain memory allocations after the current DRI process released its lock on the device, so any data uploaded to the graphics memory such as [[Texture mapping|textures]] were lost for upcoming operations, causing a significant impact on graphics performance.

Nowadays DRI1 is considered completely obsolete and must not be used.