I'm just having a bit of a thought here...

My graphics card has two dvi outputs, to which I have connected two monitors. When I run things at fullscreen, I often see stuff rendered on the second monitor. Screensavers, for example, span both monitors, and if the second one is off it is clear that the first one is still displaying an image designed for two full screens.

Since my second monitor is turned off most of the time, this seems like it is a waste of the graphics card's processing power. Should I disable the second monitor entirely when I don't plan on using it? Or is the graphics card not actually transmitting anything to the turned-off monitor? Or perhaps it's always going to output the two signals regardless of what I connect/set, so it doesn't matter?

Unless you're running off a battery, I really can't see what difference it would make...

if you have different contents on the monitors, yes, i would turn it off when not in use. why? because i'd lose my mouse over to it and won't see where it is.

Well for one thing, it would cut down on my energy bill to no longer be outputting to an unused monitor. It would also reduce the load on the card, which might lengthen it's lifetime. Right?

Yes. If you're not using the second monitor, disable it from your video settings so that your PC doesn't do the extra work of outputting a video signal to it (after calculating all the pixels for it).

damn! they should really make it detect that automatically

I disagree.

Why? A simple handshake with the secondary port would ensure minimal energy usage and would reduce load on the card when applicable. The primary port could still be always-active so that you don't run into the situation where you can't get the card to display anything...

What about cards (most that I know of, at least from the last few years) that permit connecting a single display to either of the output ports?