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View Full Version : Can you run multiple computers off 1 power supply?



pantera989
25-03-2009, 05:35 PM
Is there a form of splitter so I could run 5 or so low power mini itx systems (50W max draw each) from one standard ATX power supply?

Speedy Gonzales
25-03-2009, 05:37 PM
I doubt it

hueybot3000
25-03-2009, 06:14 PM
I doubt it

Why not? It wouldnt be overly difficult. The only way i could see it working though is that all the computers are running at the same time, and you would have to have a master computer that powered them up

Im no electrician but couldnt you split the connector wires into 5 and if you were using a modular psu you could use them to run various drives etc

Speedy Gonzales
25-03-2009, 06:17 PM
Try it and find out. See what happens

You would have to connect more than the power to get one going.

How would you do that?

pantera989
25-03-2009, 06:24 PM
All turning off and on at the same time is perfectly fine.
I've considered making my own PCB up or something, but finding 5 or so of the 24 pin connectors might be trouble and a suitable board to make it on ( all the ones at Dicksmiths are very thin copper and I don't think would be able to take the current), I just don't know how the turn on/off bit would work.

hueybot3000
25-03-2009, 06:32 PM
If you do go ahead with this post pics cos im pretty interested in it, try jaycar if theres one in your area, they have better quality boards and might even sell the 24pin connnectors

To turn if on you would have to use one computer which turns on and then it would have to flick a relay or something that turned on power for the other computers. Turning off safely could be difficult though

pantera989
25-03-2009, 06:49 PM
Connecting the green wire (on) to any ground will turn the power supply on, would this therefore turn all the motherboards on?

As for jaycar, im finding there website really hard to navigate, do you happen to know if they sell pre-printed PCBs similar to bread boards?

hueybot3000
25-03-2009, 06:52 PM
should do yeah, so you could hook them all up to master button

im pretty sure they do sell preprinted boards but not sure of the range. you could probaly use a board from an old psu. at least that way u know itd be upto it

pantera989
25-03-2009, 06:55 PM
With a master switch would that mean that the only way to turn it off the separate motherboards would be to kill the power supply as opposed to using the OS to do so?

hueybot3000
25-03-2009, 06:56 PM
yeah well i guess youd have to, unless you coud find a plugin for whatever os your using to disable soft power off, like back in the windows 98 days

hueybot3000
25-03-2009, 06:59 PM
but then that would only work if each computer had its own switch.

Actually you could do it without a master switch, if its just an extension of the psu's orignal cables then you could have each computer seperate, youd just have to isolate each computer individually from whatever tells the psu to turn on. Am i making any sense lol???

pantera989
25-03-2009, 07:01 PM
Well if i get round to building something i will post some pics. Planning to build a small mini itx cluster, mostly to learn how to use some software as opposed to actually building a powerful useful cluster.

hueybot3000
25-03-2009, 07:03 PM
good luck with it, il talk to my dad when i next see him, hes into that sorta stuff

pantera989
25-03-2009, 07:06 PM
Yeah i see what you are saying. The power switch on your computer plugs into the MB, which turns the PSU on, does the power supply unit turning on, turn the computer on, or the pressing of the switch?

hueybot3000
25-03-2009, 07:41 PM
pressing the switch does something that starts up the psu, obviously the psu isnt always on, its whatever switches the power to the mobo on that you want to tap into

pantera989
25-03-2009, 08:14 PM
Well when you press the on switch something in the Mother board connections the green wire in the power supply to a ground which turns the power supply on, i just don't no what turns the motherboard and cpu and all that on, the switch being pressed or the power coming on.

Speedy Gonzales
25-03-2009, 08:32 PM
Well the ATX 20-24 pin connector will deal with most of it.

And the power connector header on the mobo (since this is what the front of a case, is connected to). So, when you press the button on the front, it turns the system on.

You could probably wire / join the power connector from the 1st to the last mobo. But the main prob, would be supplying the power (from the ATX 20-24 pin connector), to the rest of the mobos. With only 1 PSU.

hueybot3000
25-03-2009, 10:27 PM
well you would splice into the 24 in connector i would of though, as long as the psu is well up to the task it should be fine

Rob99
25-03-2009, 11:31 PM
Its the purple wire that will fire up the PSU when bridged to black.

Agent_24
26-03-2009, 01:31 AM
Its the purple wire that will fire up the PSU when bridged to black.

Fire is definitely the correct word there...

pantera989
26-03-2009, 08:16 AM
Its the purple wire that will fire up the PSU when bridged to black.

I've been starting PSU's for years by putting a wire between the green, and any ground (black) for filling up water cooling systems, it is also stated as green here http://en.wikipedia.org/wiki/ATX

Infact ive never seen a purple wire on a PSU before.

Chilling_Silence
26-03-2009, 09:02 AM
You could also get around the "Powering up one PC at a time" issue by using something such as Wake on LAN? :)

Technically speaking I dont see why it *shouldnt* be possible. I know that the likes of the Atom 230 boards we've been using draw ~35w, bearing in mind that HDD's (I use CF Adapters) draw power also, but if you've got 4-5 on a 500watt PSU it'd be an interesting exercise to say the least! :)

Agent_24
26-03-2009, 12:43 PM
I've been starting PSU's for years by putting a wire between the green, and any ground (black) for filling up water cooling systems, it is also stated as green here http://en.wikipedia.org/wiki/ATX

Infact ive never seen a purple wire on a PSU before.

On a standard PSU with standard colour-coding the purple wire is the 5v standby line. Shorting this to ground would definitely "fire" the PSU up...

If your PSU doesn't have a purple wire it's probably made by someone like Dell/HP (and may likely have a different pinout because those companies are oh-so-special) etc or it's just built by someone who thinks that having different colour-coding but a normal pinout is fun. :illogical

pantera989
26-03-2009, 01:26 PM
"or you want to use an ATX power supply to power other devices (such as hard drives), you can short the green wire to one of the black wires"

Source: www.IBM.com

As long as the PSU is powered from the mains, it is also providing your motherboard with a small amount of power from a connector known as the +5VSB (pin 9 of the motherboard connector, connected to a purple wire), or five volt standby. Even though your system is powered down, you are still drawing a small amount of current from this. The circuits that control the power switch are among the things using that power. When you press the power button, you momentarily close a set of contacts. The motherboard circuity reacts to that signal by sending a signal to the PSU. The signal is called the PS_ON# (pin 16 of the motherboard connector, connected to a green wire), and the setting of a LOW voltage (0V) on this connector tells your PSU to deliver full power to your system

Source: http://case-mods.linear1.org/

Erayd
26-03-2009, 02:34 PM
You could also get around the "Powering up one PC at a time" issue by using something such as Wake on LAN? :)
This won't work - WOL still switches the PSU on and off, so send a WOL command to one and they'd all come on. Oh and if you shut one down, either they'll all switch off, or the one you just shut down may reboot instead.

Something else nobody seems to have mentioned yet is the fact that the output capacity of a PSU isn't all aggregated into one channel. While it may in fact be capable of delivering 500W of output, that output isn't going to be distributed evenly. Each output voltage and channel will receive a different proportion of that (e.g. maybe 10W standby line, 70W 3.3v lines etc). As a result, the number of systems you can simultaneously power off one PSU is limited to the number the 'weakest link' circuit is capable of driving.

My guess is you won't have nearly enough capacity to do what you're wanting on the standby and 3.3v channels, but will have far too much on the 5v and 12v channels - particularly 12v.

Erayd
26-03-2009, 02:51 PM
Oops, last sentence of the above post should say "...particularly 5v."

pantera989
26-03-2009, 04:39 PM
Yeah I would have to be careful when buying the PSU and check its spec sheets to make sure there's enough power on the right Voltages