The video in the MVP4 is in the "North Bridge" chipset,
which is the VIA VT82C501. It has a Trident 9398DVD video unit in it
The PCI Device ID of the video unit is 1023:8400
1023:8400 is also the PCI ID of the trident CyberBlade i7.
Apparently the CyberBlade i7 is the chipset in the mobile version of the VT82C501, but it's different than the 9398DVD in non-mobile versions.
If you have the non-mobile version, use
Chipset "blade3d"in the "Device" section of your XF86Config-4 file.