There are still problems with graphics corruption on my Mystique card which were
introduced in XFree86 4.4 - see http://bugs.xfree86.org/show_bug.cgi?id=1313

My card is rev. 2:
00:14.0 VGA compatible controller: Matrox Graphics, Inc. MGA 1064SG [Mystique]
(rev 02) (prog-if 00 [VGA])
        Subsystem: Matrox Graphics, Inc. MGA-1084SG Mystique
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping+ SERR- FastB2B-
        Status: Cap- 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
        Latency: 64
        Interrupt: pin A routed to IRQ 11
        Region 0: Memory at e0000000 (32-bit, non-prefetchable) [size=16K]
        Region 1: Memory at e1000000 (32-bit, prefetchable) [size=8M]
        Region 2: Memory at e2000000 (32-bit, non-prefetchable) [size=8M]
        Expansion ROM at <unassigned> [disabled] [size=64K]


This fixes the problems:
--- xc/programs/Xserver/hw/xfree86/drivers/mga/mga_storm.c~     2004-12-28 18:2
+++ xc/programs/Xserver/hw/xfree86/drivers/mga/mga_storm.c      2004-12-28 18:2
@@ -1077,7 +1077,7 @@
     CHECK_DMA_QUIESCENT(pMga, pScrn);

     /* MGAISBUSY() reportedly causes a freeze for Mystique revision 2 and olde
-    if (!(pMga->Chipset == PCI_CHIP_MGA1064 && (pMga->ChipRev >= 0 && pMga->Ch
+    if (!(pMga->Chipset == PCI_CHIP_MGA1064 && (pMga->ChipRev >= 0 && pMga->Ch
        while(MGAISBUSY());
     /* flush cache before a read (mga-1064g 5.1.6) */
     OUTREG8(MGAREG_CRTC_INDEX, 0);