Working with bad video memory

[Greg Michalec]

Hi -
I have an emachines m6805 laptop with integrated Mobility Radeon 9600 
M10 (RV350) running Ubuntu 7.10. I'm pretty sure my video ram has 
recently failed somehow. I could see the boot process fine, but upon 
enter X, the screen would black out, and sometimes the machine would 
hang. Even odder things happen when I try booting into that other OS 
(XP) in anything but "safe mode". I was limping along using the VESA 
driver (running 1024x768 on my 1280x800 widescreen :( ), until I decided 
to try setting the GARTSize option in xorg.conf to "0" - and it worked! 
I'm back running native resolution, using the ati driver! However, i 
think because I have no video memory enabled, i'm unable to get DRI.
My question is mostly academic, as really the only benefit to having DRI 
I can see would be to have compiz work again, but here it is:
1) Is there any way to test the video ram to see how much of it has gone 
bad?
2) If so, is there anyway to use the good stuff and avoid using the good 
stuff.
I know such workarounds exist for system memory, so I'm wondering if 
it's possible to do with video memory as well.

Thanks for any advice people can give, and a great big thanks to all 
those involved in making X.org flexible and easy to configure enough to 
allow me to get this far!

--greg michalec