try the following
knoppix screen=1024x768 vsync=90 hsync=75

on the monitor I was using before it finally died I had to use
knoppix screen=1024x768 vsync=60 hsync=60
knoppix's default is 1280x1024, my monitor only went to 1024x768.
my monitor wouldn't lock onto vsync above 60.
( should have, but wouldn't.....)
any vga monitor should work at 800x600 vsync=60 hsync=60

.... unless the smoke got out of one of the parts.....