UXA
Intel's 2008 rewrite of EXA, built on the observation that integrated graphics has no memory of its own to move pixmaps into.
EXA's chronic headache was deciding which pixmaps belonged in video memory and which in system memory, then shuffling them back and forth. On Intel's integrated graphics the whole question was moot: the GPU reads the same RAM as the CPU. UXA, the UMA Acceleration Architecture after Unified Memory Architecture, kept EXA's interface to the driver and dropped the migration. Every pixmap became a buffer object in GEM, the kernel memory manager Intel was building at the same time.
UXA only ever lived in xf86-video-intel; no other driver picked it up. Nor was it meant to last. Intel replaced it with SNA a few years later, and most distributions have since skipped both in favour of modesetting and Glamor.