It sounds as though you are using the monitor in the overscan mode. This is
exactly how a television set operates--a portion of the video display is
off the screen. This is not a problem when watching television but it is a
serious inconvenience when using a NTSC receiver (TV) as an output to a
computer generated signal. The solution is to operate the TV in the
underscan mode. To do this you must open the monitor control panel and
select the lower resolution (512 x 384) via the options button. This is
the underscan mode and will allow you to see the entire raster when you
"switch" to the TV.
Using the S-video output from the computer to drive an S-video
compatible monitor will provide a slightly improved signal. However, the
improved performance is very subtle and may not even be discernible under
certain displays.
Finally, because of the almost endless number of third party monitors in
the marketplace, Apple does not keep track of nor maintain a list of those
which may or may not be compatible with our ever growing CPU line. I
recommend you contact the individual vendors who will inform you as to
their compatibility with a particular Apple computer.