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Hi,

regarding motherboards:
I have some rigs sitting on wood, I guess I should ground the motherboard to the PSU case, right? i guess if i throw a cable between some mounting hole to the psu case it will be enough...


regarding psus:
If I have several PSUs to feed a single rig, I guess I should ground them together, how to do so properly? a single cable connected between the two psu cases will be enough?

Everything is grounded already. Please dont connect some random stuff with each other.

The PSUs are grounded through the power cable from the wall and all the hardware is grounded through the power cables coming from the PSU. Connecting a mounting hole to the PSU case could only trigger "Case Open" detection some mainboards have and thats useless....or in worst case you create a short somehow and break something with the addiditonal cables added.

Just watch out not to mix stuff up and power each piece completely from the same PSU (e.g. Riser + GPU from same PSU, CPU Power + ATX power from same PSU etc.)

^
What Greeny said is all you need to know.

Ok, thanks.

So only thing is to have all gpus powered by the same PSU but I can power GPU0-2 with one PSU and GPU4-6 with other PSU right?

I wonder why there are a lot of threads about grounding PSUs together ...

Exactly, power the riser and the GPU in that riser from the same PSU and it should be fine. Like this: PSU1: ATX, CPU, GPU0 in x16 slot, GPU1, Riser 1 PSU2: GPU2, Riser 2, GPU3, Riser3 etc.


Honestly, I havent seen a single thread discussing that but im new here ;D I can think of two reasons where you would talk about such a thing:

1. The basic principle is having a common ground for all electrical loads together. If you look at your entire rig as one circuit then you might consider connecting grounds. But if you connect a GPU and its riser to PSU2 then you have an independent circuit as none of the consumers is connected to PSU1 and therefor dont need to connect grounds.

2. To power on the 2. PSU you have to ground a pin on the ATX plug (thats what usually the power on switch does when you press it...but thats connected to PSU1 so you have to forward that signal somehow to PSU2). People use an "add2psu" thing for that.

Here is where you want to worry about grounds:

1) Your outlet is properly wired: http://www.homedepot.com/p/Commercial-Electric-Tools-Outlet-Tester-Green-MS112H/206029154

2)  If your rigs are in a carpeted area and walking on the carpet generates static electricity, then I would consider grounding the frames that hold the wood shelf.

3) If you have an professional electrician around, ask them to check the grounding of the main panel.

Typically a MB on wood is not bad because the wood shelf is in a metal frame and the metal frame is on concrete. Any excess charge buildup on the MB is bled off by the wood which in turn is bled off by the metal frame into the concrete foundation.

As mentioned above, there is really no need to internally ground the guts together because that has been engineered in already, but proper grounding of the power supply could be an issue if you are located in a dodgy facility or dwelling.


Here is the last word on grounding and sensitive electronics: https://www.tek.com/document/handbook/low-level-measurements-handbook   for people for whom the phrase, anally geeky, may apply.

Thanks, I understand.

my outlet is properly wired, I tested it with a multimeter and an electrician did install a new power line for my rigs. So there is no problem with my outlets :)

So I guess I shouldnt worry about it

While you should power all of the motherboard power plugs (24 pin, 8 pin, and all supplementary) off of one PSU, you do NOT need to power risers and video cards off of the same power supply. You just dont.

Im confused. Can we get a final consensus on what really is necessary? Ive actually seen some people say that you should power your riser and mobo from the same PSU and then forget about which PSU runs the GPUs. Of course this would all be simple and easy if you just got a power-efficient server PSU in the first place.

He hit the nail on the head!! Good answer!!

More than one ground path = ground LOOP which CAUSES issues.

 BAD IDEA.

 It's not an issue in cases because the points where the hold-down screws go into the motherboard are ISOLATED electrically from anything else.


 As others have already said, the MB is grounded through the ground leads to the power supply.