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Multiple solution

Hi

Google is your friend : http://www.laissemoichercherca.com/?q=multiple%20psu

first link  ;)

Not if you do it correctly and the PSU are the newer/better units. Make sure the PSU connected to the same systems are on the same ground, usually plugging them into the same power strip/socket is fine.

Some PSU might not work with zero load on the +5V and +3.3V line so you might want to plug one into the motherboard and the other one to the HDD to put a load on the +5V/3.3V circuit. The newer ones shouldn't have a problem but I don't know what those PSU you have might be, better to be safe than sorry.


In this case, it might be better to mix
800W -> board, Card 1, Card 2
550W -> Card 3, Card 4

The reason is to distribute the load so that both PSU loaded as lightly relative to their max capacity.

Assuming your board draws about 100W and each card draws 200W, this would give a 500/800 (62.5%) and 400/500(72%). Although it's more likely going to be a 68%/70% thing since card 3/4 would still draw some power through the PCI-e connector, you'll have to use a clamp ammeter to find out the actual split to optimize.

Going your original route, you'll end up with 300/550 (54.5%) and 600/800 (75%) which makes the 800W operate at lower efficiency and so cost slightly more in terms of electricity.

http://www.overclock.net/power-supplies/14455-multiple-power-supply-guide.html

here is what you want (I hope so)

Cost wise you are correct, but some people don't want to spend the time and potentially mess up their rigs with multiple PSU's. Also there is a heat issue you will have 3 power supplies spinning out hot air versus 1 and for me its aesthetically displeasing to have 3 power supplies for each setup I have rather just have the one. Keeping in mind I am limited on physical space where I am staying and its already pretty hot right now with the rigs I have.

Nevertheless one day I will try to rig some cheaper PSU's together just to try it out and see how it works out.

For one thing it's more troublesome, one loose wire and the secondary PSU stops, then your whole setup would likely crash or at least the card will start screaming. For another, not everybody is comfortable with the idea of an expose PSU next to them. Some think it's ugly and most just don't realize it can be done.

3 PSU running at optimal loading will put out less hot, in terms of total heat energy, air than 1.

That article describes how to do it so the second supply is "independent" but I think around here I have also read an alternate "dependent" connection mode. Instead of connecting the green to black so it's always on, you can tie the grounds (black) from one supply to the other and then connect the greens together. This way when the main supply powers on the second one also follows it.

Grounding the "PWR-ON" (green) signal turns both on since they are connected together.

If I'm wrong about this please let me know as I was planning this connection for my next system in a couple weeks.

To your comment about this beign to easy. Yes it is, but people are scared of what they do not understand. And electricity is one of thoese things. I myself buy 500w psu for about 20usd. Then I cut the green 4th pin, and one ground and splice into my main psu that feeds into the board. Then you have a fully functional two psu design. I dont suggest more than 2 psus in the fashion. Also, use the best materials as you want to avoid fire/damage

Yup, tying the two green or Pin 14 to be technically exact together will turn both PSU on when you hit the power button for the motherboard connected PSU. Don't think you need to tie the ground together as well because they are already sharing ground (or should be!) from power cord end.

Yes that is ture. But I dont leave things up to risk

In order not to void warranty, I'd suggest not cutting the pin/wire to splice. Almost all the connectors used on the PSU allows sticking in a probe from the wire end for testing purposes. Due to this, it's quite easy to make a reversible mod by soldering a pin (or relatively stiff and narrow wire like an unbent paper clip) to each end of the splicing wire, then sticking the pins into the relevant holes on the ATX connectors. Secure with velcro strips or cable ties so that it doesn't come off accidentally.

Agreed, in these things it's better to be safe :D