Ok, so my last post was wrong. The setting in drirc does NOT sync to vblank. My latest guess is that it's not supported in the r300 branch of the radeon driver, but I can't tell for sure.
Here's the major problem again: where do I go to ask? I've checked the xorg docs, the dri wiki (who's search interface SUCKS, btw), the Fedora boards...no one seems to know. Also, forums would be GREAT for something like this, but it seems like as you trickle down deeper, you get more unsearchable listservs that require hours of browsing to look for an appropriate discussion.
That doesn't even TOUCH on the terminology issue. What's it called? Vertical blank signal? Vblank? Vertical refresh signal? Google isn't helping.
I'm frustrated.
So, I've upgraded my desktop box to Fedora 7. I like it a lot. It's mostly a bug fix/refinement release (IMHO), but there's one glaring omission: in order to run the ATI fglrx driver you have to roll back to an older version of xorg.
Not gonna happen.
Anyway, the 3D support for the open source radeon driver is getting there, but I was having trouble getting it sync'ed to vblank. Figured it out, a drirc file is necessary. It can be in /etc, or you can have a .drirc one in your home directory, but that's where you set the setting.
This page from the DRI Wiki shows an example of how to implement the vblank.
glxgears doesn't *seem* to be sync'ing based upon its output, but tearing isn't there anymore (at least not obvious tearing), so I think it works. I'll keep testing.