Two PSU: Risers-MoBo-GPU management

[Alfatta]

Hello,

If you are running two PSU (with add2psu for example) on a rig with USB Risers, should you go method A or method B?

Method A : Connect one PSU with the motherboard and all the risers and some GPU. Connect the second PSU only with GPUs
Method B : Every GPUs have to be connected to the same PSU his riser is connected, so connect every (GPU+Riser) on the same PSU. Then connect the motherboard on one of the two PSU

In other words:

Method A : "It is risky to supply the motherboard and some risers with differents PSU. But supplying a GPU and his Riser with differents PSU is ok"
Method B : "It is risky to supply a GPU and the riser connected to this GPU with differents PSU. But supplying some risers and the motherboard with differents PSU is ok"

Or also
https://i.imgur.com/eh7aOtK.png


I know this has already been discutted but it seems there is a huge controversy in this with this subject. I found a lot of people on both side claiming that the other method is really risky.
Both team have "I have already used method X and no problem" claimers (until problem). So I suppose both configurations actually work but one of them is risky while the other is the actual way to go. But I have no clue wich one

Can someone sure of himself (not just because he always tried something without a problem) help me a bit here?  

[wacko]

I think method B is a lot less risky and that's the one I use for all of my rigs.

Method A : "It is risky to supply the motherboard and some risers with differents PSU. But supplying a GPU and his Riser with differents PSU is ok"

I don't think that the motherboard has any reasons to care about how you powered the risers. You only connect them together with the data cables ("usb"), it's a very low-power connection as far as I know. A gpu, on the other hand, can draw up to 75W from the riser, and a lot more from the extra 6/8-pin pci-e connectors, so it might not like the power coming from different sources.

But I don't have (obviously ) a deep understanding of this so also interested in others' opinions.

[Set Ready Go]

I havet gone With method A for all my  rigs.
Main psu = mobo + Risers and 1 or  2 gpus.

[Alfatta]

I think method B is a lot less risky and that's the one I use for all of my rigs.

Method A : "It is risky to supply the motherboard and some risers with differents PSU. But supplying a GPU and his Riser with differents PSU is ok"

I don't think that the motherboard has any reasons to care about how you powered the risers. You only connect them together with the data cables ("usb"), it's a very low-power connection as far as I know. A gpu, on the other hand, can draw up to 75W from the riser, and a lot more from the extra 6/8-pin pci-e connectors, so it might not like the power coming from different sources.

But I don't have (obviously ) a deep understanding of this so also interested in others' opinions.

Make sense to me. Still a lot of people doesn't agree
(https://www.reddit.com/r/EtherMining/comments/6k56fv/housefire_warning_do_not_used_2_power_supplies/
https://bitcointalk.org/index.php?topic=1843586.msg18351224#msg18351224
https://bitcointalk.org/index.php?topic=1761303.msg17825999#msg17825999
https://bitcointalk.org/index.php?topic=443540.msg4878774#msg4878774
https://www.youtube.com/watch?v=pQ-EAunoAqY&t=494s around 7:15
https://miningstore.fr/fr/accueil/15-coupleur-alimentation-similaire-add2psu.html a shop site saying "Warning: do no connect motherboard or risers to the secondary PSU")
Edit: https://forum.ethereum.org/discussion/7533/its-friday-night-rig-time This, especially, is interesting