When a PC boots, it typically goes through the POST/BIOS phase where it prints things like "detecting drives" or "press any key to boot from CD" and "press F1 to edit BIOS options."
I have multiple video cards in one system (it's used for GPU computation, so there are not displays hooked up to all the cards.. some don't even HAVE a display output).
My problem is that different PCs seem to have different rules about where and if the POST screens are displayed. I may have only one display hooked up to one of 3 installed video cards, but the PC doesn't seem to find that display. This means I can't edit BIOS options or select among multi-boot OS options.
Once I boot an OS (linux or windows) there's no problem.. it's the pre-OS and bootloader phase where machines simply don't display.
What's the "rule" for display adapters during POST? Especially if there's more than one video card installed. The common sense logic of "if you have only one display hooked up, use that one" does not seem to be true.