My attempts at testing KMS on my Dell Latitude D830 (GM965) have been thwarted by persistent issues starting Xorg. Upon booting with i915.modeset=1 on the kernel command line, Xorg freezes, resulting in a black screen and unresponsive local keyboard. The machine is accessible through a serial console, although the console behaves quite strangely (serial console keystrokes aren't processed unless you hold down a key on the local keyboard). This behavior stops as soon as one breaks Xorg in gdb.

The stack backtrace shows that the x server is waiting for the drm,

Program received signal SIGINT, Interrupt.
0x0000003f7f4de037 in ioctl () from /lib64/libc.so.6
(gdb) bt
#0  0x0000003f7f4de037 in ioctl () from /lib64/libc.so.6
#1  0x00007f5a450c1183 in drmIoctl (fd=11, request=25688, arg=0x0)
    at xf86drm.c:187
#2  0x00007f5a450c1486 in drmCommandNone (fd=11, 
    drmCommandIndex=<value optimized out>) at xf86drm.c:2313
#3  0x00007f5a44c40f28 in I830BlockHandler (i=<value optimized out>, 
    blockData=0x0, pTimeout=0x7fff4db9d418, pReadmask=0x7cbc40)
    at i830_driver.c:2717
#4  0x00000000004cc3d8 in AnimCurScreenBlockHandler (screenNum=0, 
    blockData=0x0, pTimeout=0x7fff4db9d418, pReadmask=0x7cbc40)
    at animcur.c:222
#5  0x00000000004aa8c9 in compBlockHandler (i=0, blockData=0x0, 
    pTimeout=0x7fff4db9d418, pReadmask=0x7cbc40) at compinit.c:158
#6  0x000000000042aec0 in BlockHandler (pTimeout=0x7fff4db9d418, 
    pReadmask=0x7cbc40) at dixutils.c:384
#7  0x000000000043dee1 in WaitForSomething (pClientsReady=0x3cc5320)
    at WaitFor.c:215
#8  0x000000000042a550 in Dispatch () at dispatch.c:362
#9  0x00000000004243cd in main (argc=8, argv=0x7fff4db9d5f8, 
    envp=<value optimized out>) at main.c:396