Like many of you, I like to play a game every once in a while. Since I use Linux for my daily tasks (programming, writing papers, browsing, etc.), I solely exploit my graphics-card capabilities in Windows while gaming.
Lately I noticed my energy-bills got really high and I would like to reduce the energy consumption of my computer. My graphics-card uses 110 watt idle, whereas a low-end Radeon HD5xxx only uses 5 watt. I think my computer is powered on 40 hours a week, whereof only 3 hours of gaming. This means I waste 202 kWh a year (!).
I figured I could just buy a DVI splitter and a low-end Radeon-card, and disable the PCI-slot of the high-end card in Linux. I Googled a bit, but I'm not sure which search-terms to use, so I haven't found anything useful.
Too long, didn't read: Is it possible to cut of the power of a PCI-slot using Linux?
No.
What your asking isn't even a "Linux" question, but a motherboard question - is it electrically possible to do this.
The answer is still no.
The only chance you would have, would be to get the spec of the chip/card which is in the slot, and see if there is a bit you can set on it which would "disable" it, or put it into some "low power mode".