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.
In X.Org Server release 6.9/7.0, EXA was released as a replacement for XAA. As the X's new RENDER extension boomed, XAA can't fit the requirment very well and EXA was developped as a new architecture to support X's new RENDER extension.
VIA driver supports both XAA and EXA. When RandR extension is enabled, EXA is on by default. And when RandR extension is disabled, XAA is on by default. However, you can decide which one to use by the options below,
orOption "AccelMethod" "XAA"
Option "AccelMethod" "EXA"
or disable both.
Option "NoAccel" "TRUE"
The options belong 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.