FreeBSD 9.0 (RC2),
ASUS P9X79 motherboard, Intel i7-3930k,
Diamond Radeon HD 6708, ASUS VS228 monitor.
Because FreeBSD does not support KMS (The only modern OS not to), I have to use the vesa driver. The monitor supports 1920x1028.
# xrandr
Screen 0: minimum 320 x 200, current 1280 x 1024...