G'day folks, I have an IBM P70 (Type 6554-674) that no matter what
display mode I choose, (640*480 - 1600*1280), it always has approx.
30-35mm of each side of the screen unused when the horizontal size is
adjusted to %100. Vertical size is fully adjustable to the viewable
area limits.

I've tried different computers, (including one that will allow me to set
vert/horiz. frequencies other than the standard, the full range that the
monitor is capable of), and it still will not allow a full width picture.

If I turn up the brightness sufficiently I can see the raster edges end
approx 20-25mm from the edges of the viewable area, with the output
display ending approx 15mm short of that, if you know what I mean.
The output display is fully positional within the raster area.

Crappy ASCII pic follows, (haven't bothered showing top/bottom):

Screen edge Screen edge
v v
| 20 |15| |15| 20 |
| mm |mm| Display |mm| mm |
| | | output | | |
^ ^
Raster edge Raster edge

Would this possibly be because of reduced horizontal drive?

I have a Service Manual for the GDM-17SE2T, (has some minor control
differences), but before I got into the guts of the thing I was
wondering if anyone had any ideas?

TIA,
Dave