Comment 5 for bug 1316035

Activating EXA
Section "Device"
        Identifier "mga"
        Driver "mga"
        Option "AccelMethod" "EXA"
        Option "EXANoComposite" "True"
        Option "EXANoDownloadFromScreen" "True"
        Option "EXANoUploadToScreen" "True"
Endsection

makes it worse than normal software render.

It results in hanging X without disabling Compsite/DownloadFromScreen. Disabling Composite, DownloadFromScreen results in fully corrupted screen, disabling UploadToScreen helps a little, however screen is still corrupted (moving a window over another leaves traces in the inactive windows behind).

The remaining acceleration
[ 268.727] (**) MGA(0): EXA: Disabling Composite operation (RENDER acceleration)
[ 268.727] (**) MGA(0): EXA: Disabling UploadToScreen
[ 268.727] (**) MGA(0): EXA: Disabling DownloadFromScreen
[ 268.727] (II) EXA(0): Offscreen pixmap area of 8474624 bytes
[ 268.727] (II) EXA(0): Driver registered support for the following operations:
[ 268.727] (II) Solid
[ 268.727] (II) Copy
[ 268.727] (==) MGA(0): Backing store enabled

is just as slow as normal render => EXA + matrox card is not usable