Does a OS reboot affect the PSU?

[LibertySyclone]

Long story short I am trying to run 3-4 mobos off of a single power supply (Intel Avaton C2550s so not very much power draw) They will be ESXi nodes for my traveling test lab.

I would really like to be able to reboot them individually if needed without disturbing the other 2-3 boards. But I am unsure of what happens to the PSU during the rebooting process?

My initial thought would be to have something like a Raspi control the Pwr On signal, and from what I am reading I could then send each motherboard the PWR OK signal from the Rpi or an Arudino. Because the Mobos shouldn't turn on w.o that signal even if they are receiving full power on the 12/5/3.3 lines?

I am worried about the 3.3v signal as well. not sure if I would need to separate it from the motherboards or not. Although I think its just a "health/heartbeat" signal from the PSU?

 

[GiGaBiTe]

Unless the motherboard stops shorting the power on (green) wire to ground, then the power supply will keep running if the motherboard reboots.

The "Power OK" wire is just a read only signal from the PSU to the motherboard telling the motherboard that the voltages from the PSU are at a safe level to operate. There is just one of these "Power OK" wires for all the outputs, and there's no communication over it. It's just a fixed voltage if good or no/low voltage if bad.

As for what you're doing, I don't really think it's a good idea. Motherboards inject stray signals back into the power rails, which can potentially cause problems. If you plug in an unfiltered audio amplifier to the same power supply as a motherboard, you can hear all sorts of horrible stuff on the power rail.

I'd recommend something safer like a PicoPSU:

http://www.amazon.com/Mini-Box-picoPSU-160-XT-Power-Mini-ITX-Supply/dp/B005TWE6B8

You can wire up the power input side to like a PCIe power connector and put a switch in there to turn it on and off.

 

[FnordMan]

As for what you're doing, I don't really think it's a good idea. Motherboards inject stray signals back into the power rails, which can potentially cause problems. If you plug in an unfiltered audio amplifier to the same power supply as a motherboard, you can hear all sorts of horrible stuff on the power rail.

I'd recommend something safer like a PicoPSU:

http://www.amazon.com/Mini-Box-picoPSU-160-XT-Power-Mini-ITX-Supply/dp/B005TWE6B8

You can wire up the power input side to like a PCIe power connector and put a switch in there to turn it on and off.

Seconded, one PSU to a bunch of motherboards sounds like a bad idea to me. Get a bunch of the +12VDC input PicoPSUs and wire them all up to input from one central PSU.
From there you just force the central PSU to be on.
Note that if you don't need that much capacity (160W on the linked one) there's cheaper ones over on mini-box.com.

 

[michalrz]

Thirded (?). Very bad idea. So many different devices connected in parallel will mess up the way PSU currents will 'distribute' themselves.
Certain signals from the PSU might not reach all boards and vice versa.
Four Gigahertz-switching regulators operating with a common ground and power might cause coil whine hell.

 

[Millerboy3]

Add another fo the picopsu's they are awesome! used some of these for a few projects and they work suprisingly well