I don't know if this is of any help, but I had an old Radeon 8500LE (OEM ATI) that would only output s-video once Windows booted up. (It was black during boot-up and I couldn't enter BIOS with it). When I picked up a Radeon 9800 I was surprised to see s-video booted quicker than my monitor and BIOS and everything was visible. Not sure if this helps. Maybe DOS is different, or maybe the card was just slightly defective, but just throwing it out there.