Description of problem:

I'm developing some games and 3D apps and I discovered a weird thing.
The frames per second vary according to the resolution, of course.
But when I use a windowed resolution of 896x500 I got about 70 fps.
When I change to 897x500 the fps drop to 7~8. I don't think that's normal!

How reproducible:
I just use SDL creating a context like that:

SDL_SetVideoMode(WIDTH,HEIGHT,16,videoFlags); and so on
if width is 896 or less everything it's ok, but when it's 897 or greater the performance drops to an usable app.

Additional info:
Here goes the xorg.conf and the glxinfo:

server glx vendor string: SGI
server glx version string: 1.2
server glx extensions:
client glx vendor string: SGI
client glx version string: 1.4
client glx extensions:
OpenGL vendor string: Tungsten Graphics, Inc
OpenGL renderer string: Mesa DRI Intel(R) 945GM GEM 20090114 x86/MMX/SSE2
OpenGL version string: 1.4 Mesa 7.5-devel



xorg.conf: 

Section "ServerLayout"
	Identifier     "X.org Configured"
	Screen      0  "Screen0" 0 0
	InputDevice    "Mouse0" "CorePointer"
	InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "Files"
	ModulePath   "/usr/lib/xorg/modules"
	FontPath     "catalogue:/etc/X11/fontpath.d"
	FontPath     "built-ins"
EndSection

Section "Module"
	Load  "extmod"
	Load  "record"
	Load  "glx"
	Load  "dri"
	Load  "dri2"
	Load  "dbe"
EndSection

Section "InputDevice"
	Identifier  "Keyboard0"
	Driver      "kbd"
EndSection

Section "InputDevice"
	Identifier  "Mouse0"
	Driver      "mouse"
	Option	    "Protocol" "auto"
	Option	    "Device" "/dev/input/mice"
	Option	    "ZAxisMapping" "4 5 6 7"
EndSection

Section "Monitor"
	Identifier   "Monitor0"
	VendorName   "Monitor Vendor"
	ModelName    "Monitor Model"
        Option  "Tiling" "Off"
        Option "AccelMethod" "XAA"

EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz"
        ### [arg]: arg optional
        #Option     "NoAccel"            	# [<bool>]
        #Option     "SWcursor"           	# [<bool>]
        #Option     "ColorKey"           	# <i>
        #Option     "CacheLines"         	# <i>
        #Option     "Dac6Bit"            	# [<bool>]
        #Option     "DRI"                	# [<bool>]
        #Option     "NoDDC"              	# [<bool>]
        #Option     "ShowCache"          	# [<bool>]
        #Option     "XvMCSurfaces"       	# <i>
        #Option     "PageFlip"           	# [<bool>]
	Option	"Tiling" "Off"
	Option "AccelMethod" "XAA"
	Identifier  "Card0"
	Driver      "intel"
	VendorName  "Intel Corporation"
	BoardName   "Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller"
	BusID       "PCI:0:2:0"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Card0"
	Monitor    "Monitor0"
	SubSection "Display"
		Viewport   0 0
		Depth     1
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     4
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     8
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     15
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     16
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     24
	EndSubSection
EndSection




My app isn't strange. It doesn't use lighting and stencil and those strange extensions. I tested two apps at the time.
It all worked like a charm a week ago with a fully updated Fedora 10.