I've just tried using EXA accel instead of UXA with the latest PPA drivers :

- glxgears reports 550-590 FPS with EXA where it would report about 230 FPS with UXA.

- ppracer is smooth and fun with 25-30 FPS with EXA where it would be 3 to 5 FPS with UXA.

- I haven't yet had time to investigate if it has other impacts on system stability or graphics artifacts, but at least the perf gain is huge. Not seen any "screen flash" so far.

- I've noticed a weird scratching and "FFFRRRRRTTTTT !" noise in system speakers during KDE session start, which I had never noticed before, afterwards sound seems to work normally.

- My xorg.conf says :

Section "Device"
        Identifier      "Configured Video Device"
        VideoRam        262144
        Option          "AccelMethod"                   "exa"
        Option          "EXAOptimizeMigration"          "true"
        Option          "MigrationHeuristic"            "greedy"
EndSection

- I'm calling fixmtrr.sh from /etc/rc.local and /etc/X11/xinit/xserverrc (not sure if KDM uses it or ignores it)

- my X log says (some possibly interesting parts only) :

X.Org X Server 1.6.0
Release Date: 2009-2-25
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.24-23-server i686 Ubuntu
Current Operating System: Linux xtro 2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:57:59 UTC 2009 i686
Build Date: 09 April 2009  02:10:02AM
xorg-server 2:1.6.0-0ubuntu14 (<email address hidden>)
(--) PCI:*(0@0:2:0) Intel Corporation Mobile 945GME Express Integrated Graphics Controller rev 3, Mem @ 0xfbd00000/524288, 0xd0000000/268435456, 0xfbcc0000/262144, I/O @ 0x0000dc80/8
(II) Open ACPI successful (/var/run/acpid.socket)
(II) System resource ranges:
        [0] -1  0       0xffffffff - 0xffffffff (0x1) MX[B]
        [1] -1  0       0x000f0000 - 0x000fffff (0x10000) MX[B]
        [2] -1  0       0x000c0000 - 0x000effff (0x30000) MX[B]
        [3] -1  0       0x00000000 - 0x0009ffff (0xa0000) MX[B]
        [4] -1  0       0x0000ffff - 0x0000ffff (0x1) IX[B]
        [5] -1  0       0x00000000 - 0x00000000 (0x1) IX[B]
(==) AIGLX enabled
(II) Matched intel from file name intel.ids
(==) Matched intel for the autoconfigured driver
(==) Assigned the driver to the xf86ConfigLayout
(II) LoadModule: "intel"
(II) Loading /usr/lib/xorg/modules/drivers//intel_drv.so
(II) Module intel: vendor="X.Org Foundation"
        compiled for 1.6.0, module version = 2.7.99
        Module class: X.Org Video Driver
        ABI class: X.Org Video Driver, version 5.0
(II) intel: Driver for Intel Integrated Graphics Chipsets: i810,
        i810-dc100, i810e, i815, i830M, 845G, 852GM/855GM, 865G, 915G,
        E7221 (i915), 915GM, 945G, 945GM, 945GME, IGD_GM, IGD_G, 965G, G35,
        965Q, 946GZ, 965GM, 965GME/GLE, G33, Q35, Q33,
        Mobile Intel® GM45 Express Chipset,
        Intel Integrated Graphics Device, G45/G43, Q45/Q43, G41
(II) Primary Device is: PCI 00@00:02:0
(II) resource ranges after xf86ClaimFixedResources() call:
        [0] -1  0       0xffffffff - 0xffffffff (0x1) MX[B]
        [1] -1  0       0x000f0000 - 0x000fffff (0x10000) MX[B]
        [2] -1  0       0x000c0000 - 0x000effff (0x30000) MX[B]
        [3] -1  0       0x00000000 - 0x0009ffff (0xa0000) MX[B]
        [4] -1  0       0x0000ffff - 0x0000ffff (0x1) IX[B]
        [5] -1  0       0x00000000 - 0x00000000 (0x1) IX[B]
(II) resource ranges after probing:
        [0] -1  0       0xffffffff - 0xffffffff (0x1) MX[B]
        [1] -1  0       0x000f0000 - 0x000fffff (0x10000) MX[B]
        [2] -1  0       0x000c0000 - 0x000effff (0x30000) MX[B]
        [3] -1  0       0x00000000 - 0x0009ffff (0xa0000) MX[B]
        [4] 0   0       0x000a0000 - 0x000affff (0x10000) MS[B]
        [5] 0   0       0x000b0000 - 0x000b7fff (0x8000) MS[B]
        [6] 0   0       0x000b8000 - 0x000bffff (0x8000) MS[B]
        [7] -1  0       0x0000ffff - 0x0000ffff (0x1) IX[B]
        [8] -1  0       0x00000000 - 0x00000000 (0x1) IX[B]
        [9] 0   0       0x000003b0 - 0x000003bb (0xc) IS[B]
        [10] 0  0       0x000003c0 - 0x000003df (0x20) IS[B]
(**) intel(0): Option "AccelMethod" "exa"
(II) intel(0): Integrated Graphics Chipset: Intel(R) 945GME
(--) intel(0): Chipset: "945GME"
(--) intel(0): Linear framebuffer at 0xD0000000
(--) intel(0): IO registers at addr 0xFBD00000
(WW) intel(0): libpciaccess reported 0 rom size, guessing 64kB
(**) intel(0): Using EXA for acceleration
(II) intel(0): 2 display pipes available.
(II) Loading sub module "exa"
(II) LoadModule: "exa"
(II) Loading /usr/lib/xorg/modules//libexa.so
(II) Module exa: vendor="X.Org Foundation"
        compiled for 1.6.0, module version = 2.4.0
        ABI class: X.Org Video Driver, version 5.0
(II) intel(0): Comparing regs from server start up to After PreInit
(WW) intel(0): Register 0x61200 (PP_STATUS) changed from 0xc0000008 to 0xd000000a
(WW) intel(0): PP_STATUS before: on, ready, sequencing idle
(WW) intel(0): PP_STATUS after: on, ready, sequencing on
(WW) intel(0): Register 0x71024 (PIPEBSTAT) changed from 0x80000202 to 0x80000242
(WW) intel(0): PIPEBSTAT before: status: FIFO_UNDERRUN VSYNC_INT_STATUS VBLANK_INT_STATUS
(WW) intel(0): PIPEBSTAT after: status: FIFO_UNDERRUN VSYNC_INT_STATUS LBLC_EVENT_STATUS VBLANK_INT_STATUS
(WW) intel(0): DRI2 requires UXA
drmOpenDevice: node name is /dev/dri/card0
drmOpenDevice: node name is /dev/dri/card0
drmOpenByBusid: Searching for BusID pci:0000:00:02.0
drmOpenDevice: node name is /dev/dri/card0
drmOpenDevice: open result is 11, (OK)
drmOpenByBusid: drmOpenMinor returns 11
drmOpenByBusid: drmGetBusid reports pci:0000:00:02.0
(II) [drm] loaded kernel module for "i915" driver.
(II) [drm] DRM interface version 1.3
(II) [drm] DRM open master succeeded.
(II) intel(0): [drm] Using the DRM lock SAREA also for drawables.
(II) intel(0): [drm] framebuffer mapped by ddx driver
(II) intel(0): [drm] added 1 reserved context for kernel
(II) intel(0): X context handle = 0x1
(II) intel(0): [drm] installed DRM signal handler
(**) intel(0): Framebuffer compression enabled
(**) intel(0): Tiling enabled
(**) intel(0): VideoRam: 262144 KB
(II) intel(0): Attempting memory allocation with tiled buffers.
(II) intel(0): Tiled allocation successful.
(II) intel(0): [drm] Registers = 0xfbd00000
(II) intel(0): [dri] visual configs initialized
(II) intel(0): vgaHWGetIOBase: hwp->IOBase is 0x03d0, hwp->PIOOffset is 0x0000
(**) intel(0): Option "MigrationHeuristic" "greedy"
(**) intel(0): Option "EXAOptimizeMigration" "true"
(II) EXA(0): Offscreen pixmap area of 12582912 bytes
(II) EXA(0): Driver registered support for the following operations:
(II)         Solid
(II)         Copy
(II)         Composite (RENDER acceleration)
(==) intel(0): Backing store disabled
(==) intel(0): Silken mouse enabled
(II) intel(0): Initializing HW Cursor
(II) intel(0): [DRI] installation complete
(WW) intel(0): drmDropMaster failed: Unknown error 4294967295
(II) intel(0): xf86BindGARTMemory: bind key 0 at 0x0edf4000 (pgoffset 60916)
(II) intel(0): Fixed memory allocation layout:
(II) intel(0): 0x00000000-0x005fffff: compressed frame buffer (6144 kB, 0x000000007f800000 physical
)
(II) intel(0): 0x00600000-0x00600fff: compressed ll buffer (4 kB, 0x000000007fe00000 physical
)
(II) intel(0): 0x00601000-0x0060afff: HW cursors (40 kB, 0x000000007fe01000 physical
)
(II) intel(0): 0x0060b000-0x0060bfff: overlay registers (4 kB, 0x000000007fe0b000 physical
)
(II) intel(0): 0x007bf000:            end of stolen memory
(II) intel(0): 0x007bf000-0x0edf3fff: DRI memory manager (235732 kB)
(II) intel(0): 0x0edf4000-0x0f9f3fff: exa offscreen (12288 kB)
(II) intel(0): 0x10000000:            end of aperture
(II) intel(0): BO memory allocation layout:
(II) intel(0): 0x007bf000:            start of memory manager
(II) intel(0): 0x00800000-0x00bfffff: depth buffer (4096 kB) X tiled
(II) intel(0): 0x00c00000-0x00ffffff: back buffer (4096 kB) X tiled
(II) intel(0): 0x01000000-0x013fffff: front buffer (4096 kB) X tiled
(II) intel(0): 0x0edf4000:            end of memory manager
(II) intel(0): using SSC reference clock of 100 MHz
(II) intel(0): Selecting standard 18 bit TMDS pixel format.
(II) intel(0): [drm] mapped front buffer at 0xd1000000, handle = 0xd1000000
(II) intel(0): [drm] mapped back buffer at 0xd0c00000, handle = 0xd0c00000
(II) intel(0): [drm] mapped depth buffer at 0xd0800000, handle = 0xd0800000
(II) intel(0): Output configuration:
(II) intel(0):   Pipe A is off
(II) intel(0):   Display plane A is now disabled and connected to pipe A.
(II) intel(0):   Pipe B is on
(II) intel(0):   Display plane B is now enabled and connected to pipe B.
(II) intel(0):   Output VGA is connected to pipe none
(II) intel(0):   Output LVDS is connected to pipe B
(II) intel(0): RandR 1.2 enabled, ignore the following RandR disabled message.
(II) intel(0): DPMS enabled
(==) intel(0): Intel XvMC decoder disabled
(II) intel(0): Set up textured video
(II) intel(0): Set up overlay video
(II) intel(0): direct rendering: XF86DRI Enabled
(--) RandR disabled
(II) Initializing built-in extension Generic Event Extension
(II) Initializing built-in extension SHAPE
(II) Initializing built-in extension MIT-SHM
(II) Initializing built-in extension XInputExtension
(II) Initializing built-in extension XTEST
(II) Initializing built-in extension BIG-REQUESTS
(II) Initializing built-in extension SYNC
(II) Initializing built-in extension XKEYBOARD
(II) Initializing built-in extension XC-MISC
(II) Initializing built-in extension SECURITY
(II) Initializing built-in extension XINERAMA
(II) Initializing built-in extension XFIXES
(II) Initializing built-in extension RENDER
(II) Initializing built-in extension RANDR
(II) Initializing built-in extension COMPOSITE
(II) Initializing built-in extension DAMAGE
(II) AIGLX: Screen 0 is not DRI2 capable
drmOpenDevice: node name is /dev/dri/card0
drmOpenDevice: open result is 12, (OK)
drmOpenByBusid: Searching for BusID pci:0000:00:02.0
drmOpenDevice: node name is /dev/dri/card0
drmOpenDevice: open result is 12, (OK)
drmOpenByBusid: drmOpenMinor returns 12
drmOpenByBusid: drmGetBusid reports pci:0000:00:02.0
(II) AIGLX: enabled GLX_SGI_make_current_read
(II) AIGLX: enabled GLX_MESA_copy_sub_buffer
(II) AIGLX: enabled GLX_SGI_swap_control and GLX_MESA_swap_control
(II) AIGLX: enabled GLX_texture_from_pixmap with driver support
(II) AIGLX: Loaded and initialized /usr/lib/dri/i915_dri.so
(II) GLX: Initialized DRI GL provider for screen 0