Why my display won't fit RS343 ?

[Fletcher Robinson]

I developed a display which uses full screen coordinates on a 4D70GT.(i.e
0,XMAXSCREEN 0,YMAXSCREEN)
Program requirements called for SGI to provide a RS-343 video modification
for my machines. I am utilizing a 25" color monitor from SRL to play my
display program. This monitor's specifications for display format and sync
timing requirements are delineated as follows :

         sync format     composite sync
         verticle field rate       60.0 hz , 2:1 interlace
         horizontal line rate      30.69 khz
         horizontal sync           2.82 microsec
         horizontal blanking       6.75 microsec
         horizontal front porch    0.75 microsec
         displayed lines           959
         total lines               1023
         verticle sync             3h (97.75 microsec)
         verticle blanking         32h (1043 microsec)
         verticle front porch      3h (97.75 microsec)
         aspect ratio              4:3
         video input level         0.7v peak to peak
         active pixels             1280

My problem is that my display program 'falls off' the screen on the
bottom and to the left of the 30hz monitor while not on the 60hz monitor
it was originally developed on. I do not think I should have to rework
the display software to fit the 30hz monitor; and making adjustments
such as verticle/horizontal sizing, etc. does not help to show more of
the display. There should be adjustments to be made on the RS-343 video
boards themselves, but I do not know where to look.

I welcome comments from anyone having any experience with this type
of problem. Thanx ...