I have a P4 LGA775 / Gigabyte 8i915MD-GV machine which has GMA 900 and I have recently updated it to 10.6.8 and made it working. Here is the link I have put up a post about this:

http://www.insanelymac.com/forum/ind...owtopic=267122

To make the long story short, what I have done is to modify DSDT and when I have put back KEXTs it worked as before and on top of that finally got list of resolutions (previously fixed to 1024x768). I had a mouse cursor issue but I have resolved that and you could find the patched AppleIntelIntegratedFrameBuffer.kext in the linked page. Only use it when you also have the cursor issue.. which would make the cursor emulating fall back to software mode to bypass the issue.

Hope it helps.