In the X Window System, XFree86 Acceleration Architecture (XAA) is a driver architecture to make a video card's 2D hardware acceleration available to the X server. But as the X's new RENDER extensions boomed, XAA can't fit the requirment very well and EXA was developped as a new architecture to support X's new RENDER extensions. In X.Org Server release 6.9/7.0, EXA was released as a replacement for XAA.

In the VIA Accelerated Linux Graphics Driver, EXA is enabled by default, though acceleration of individual functions can be switched off as needed in the server configuration file.

Option "NoAccel"       "TRUE"

This option is to disable the EXA hardware acceleration. It belongs to Section "Device".

When EXA is enabled, it's recommended to set video memory larger than 64M in BIOS settings. And the result of dimension*bpp/8 should be no larger than 8192.