The mknod commands assign kernel device numbers and file types to a filesystem entry. NVIDIA use device major 195 for their driver. Minor values 0-254 are used for individual devices, 255 is used by the driver. These device files are how user space processes, like X11, CUDA apps, OpenCL apps, etc talk to the driver. The driver can be loaded and have enumerated the hardware correctly, but if the device file entries don’t exist, user space processes have no access to the hardware. You should have something like these:
$ ls -l /dev/nv*
crw-rw-rw- 1 root root 195, 0 2011-04-02 22:55 /dev/nvidia0
crw-rw-rw- 1 root root 195, 1 2011-04-02 22:55 /dev/nvidia1
crw-rw-rw- 1 root root 195, 255 2011-04-02 22:55 /dev/nvidiactl
Note the permissions, major and minor device numbers of each (I have two cards in this particular box).
You still haven’t answered the question about what board you are using. The fact you said the ATI gpu is an onboard X1600 makes me assume this is a laptop with some sort of home brew expresscard to PCI-e adaptor hosting a desktop card. Am I warm, or should I keep guessing?