Very hot topic for me.
I have 16 SETI computers.
Together they use 1.5MwHr per month of power.
All computers are Desktop, built for speed.
Use Kill-o-watt meter to measure power use.
Lowest power computer is 67w. Runs Linux,
Has: Motherboard, CPU, Fan, floppy 256mbDDR. With network.
No: video, HD, keyboard, mouse, CD, sound
Same computer with HD, Video, running windows, uses 94watts.
I have tried to run windows disk less, cant get it to work. Also without video?
I use KVM to monitor and control all the computers.
Highest Power computer is 2.5ghz, 1gbDDR, two HD, CD, Floppy, 3 fans, Fast video + TV tuner. Uses 120 watts. All computers have UPS. Adds about 5 watts each.
Looked into 80% efficiency power supplies, cost $100 vs $13. Payoff is 80 months - years, not good. I have no idea if I will keep doing this for even 3 years.
I bought an AMD mobile processor, power is not quite half... I hope to do a little over clocking and power reduction.
The overhead of the rest of the system is high in power. A 1.6 g system and a 3 g, the power is only about 30w higher for twice the speed, stripped systems.
I plan to retire two 1.2g processors, replacing with 2.5g or higher.
The power required in a motherboard is 12v, 5v, 3.3v, 5vsb. How do you plan to use only 12v to power it?
I have considered making a Y cable for the ATX power. I plan to run up to 4 computers on one 500w PS. The efficiency goes up as the PS is loaded. I worry about doing this, it will max out the PS. The cheap PS I use, don't know how they will take it. Sometimes when the PS fail they destroy the motherboard. I have a stack of MB to prove it. And the dead PS. (8 PS in 3 years, 4 MB)
Considering using water cooling, eliminate the 2.5w fan on each processor. Problem the pump and the heat exchanger's fan will draw more power. At least it will be quieter. PC are mostly in the room where I work all day.
I will be very interested in how this turns out for you. Keep us or me posted.
Thanks for the links, a good read.
Have fun.