Low performance mesa-dri?

[Lurkos]

I realized that Etch is significantly slower than Sarge on my computer.
Is it normal?
Shall I open a bug?

Computer:
Pentium III 800 MHz
768 MB SDRAM (133 MHz)
Matrox G450 32 MB AGP (fully supported by MGA driver)

Tests with:
- same computer
- same resolution (1280x1024 at 60Hz, LCD native)
- Gnome
- Xfree86/Xorg properly configured
- DRI on

*glxgears*
- Debian 3.1 (Xfree86): 410 fps
- Debian 4.0 Live (Xorg): 320 fps (-25%)

Other tests:
*tuxracer*
Debian Sarge: usable without problems
Debian Etch: unusable (it's not fluent)
*supertux*
Debian Sarge: 59 fps (with opengl)
Debian Etch: 48 fps (with opengl)

Is it a problem of mesa package with mga cards?
Is it there a fix?
Thanks in advance.

-- 
Lurkos