http://www.emsai.net/projects/widescreen/bandwidth/
One of my favorite tools.
Over VGA you can do 3840x1024, but not over DVI.
I checked it today in windows XP 32 bit
all monitor was 19" (LG194WT/WS) 1440x900 each
hd5770 on dp @ vga adapter(single link) + matrox th2go - max I can span over 2400x600 (so 3x 800x600)
on nvidia 8600gt (dual DVI) I conected to DVI a DVI @ HDMI adapter (zotac single link) and from hdmi, HDMI to DVI cable to matrox th2go.... and the same situation, as on ati on vga :(
So conslusion:
From single link DVI or single link vga(from adapter dp @ vga)not from native vga + matrox th2go you can do max 3x 800x600 (2400x800)
too bad, now I need to buy quadro NVS 450 instead 440) :evil: