I've got a GeForce4 MX440, a AOC 9Glr 19'' CRC monitor and linux-2.6.0-test9-vanilla (but the problem doesn't change with any other 2.4 source, either). My monitor has a bug so it can't say the correct vsync to the PC; i.e. at 1024x768 I get 60Hz instead of 85Hz, producing orrible deformations. This is obviously fixed (in Windows as well as in XFree) by forcing the vsync to 85Hz. However, I haven't found any way to force it using the kernel framebuffer mode (I use vesafb). I've already read the Documentation/fb/* docs without obtaining anything. I've already tried to use the parameter "video=vesafb:1024x768-32@85" as specified in modedb.txt but it seems to be ininfluent. The fbset utility doesn't seem to have any parameter to adjust vsync frequency, either. Any suggestions?
I've never heard of a way to set vsync, but that doesn't mean one doesn't exist. You may want to try the forums, or on irc in #gentoo on irc.freenode.net
