How to correctly supply USB Powered Risers with two PSU?

[Sirvaude]

Hi there!

I'm building a mining rig (wheter it's profitable or not), my specs are:

Z77A-GD55 (Mainboard), Core i3-2100 (CPU), Corsair Vengeance 8GB (RAM), 500GB Sata (HDD), and now the problem:

I have a generic "500 Watts" (PSU), with this one, I'm pretending to supply the mainboard and HDD.

So far, the CPU works, it turns on and everything is working as expected.

The problem is... that 1st PSU won't be able to supply the 3 GPU I have (PowerColor R9 280x, Sapphire 7970, Gigabyte 7970).

So, AFAIK, I can supply those GPU with a different PSU in the 12V PCI connectors. So I buy this PSU ---> HP DPS-1200FB.

I asked before about turning on the GPU's PSU and then the mainboard PSU and there's no problem. In fact I can use a little relay to turn them both at the same time.

So yes, so far everything is OK.

But now another problem appears.

I'm using 3 of this usb risers, and now I'm not 100% sure of how should I supply them.

Some people says I must supply the usb risers with the 5v and 12v and both grounds (I mean 1 molex) from the mainboard PSU, and then only use the HP Server PSU to supply the PCI-6 and PCI-8 ports of the GPUs.

Some other people says I must get 5v and one ground from the generic PSU and 12v and the second ground from the HP PSU... to supply the mentioned risers.

I don't really know what to do, I'm afraid of damaging my GPU's. Is there anybody with experience here that can help me out?

Thanks in advance.

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[bathrobehero]

I never tried it as I always use one big good quality PSU per rig but as far as I remember reading about it long ago you have to feed each card from the same PSU on both sides.
This is because the molex going into the riser and the 6/8-pins on the GPU are not connected to the motherboard (in terms of 5V and 12V) so you're not connecting multiple PSUs to each other which would be a problem.

But wait for others who have first hand experience.

[Sirvaude]

I never tried it as I always use one big good quality PSU per rig but as far as I remember reading about it long ago you have to feed each card from the same PSU on both sides.
This is because the molex going into the riser and the 6/8-pins on the GPU are not connected to the motherboard (in terms of 5V and 12V) so you're not connecting multiple PSUs to each other which would be a problem.

But wait for others who have first hand experience.

The problem is the HP PSU only gives 12V... there's no 5V rail.

And now this: https://bitcointalk.org/index.php?topic=443540.0

I'll keep waiting.

Thanks for replying.

[bathrobehero]

Thinking about it more, the cards need 12V from both end so I don't think you need a 5V rail at all.
In fact a PCI-E slot doesn't provide 5V, only 12V and 3.3V.

The USB riser might feed itself from the PCI-E lane (3.3V) and not the 5V from the molex. Not sure though.

Edit: tried a riser with the 5V rail on the molex disconnected and it didn't work. So the USB riser does require 5v.

[Sirvaude]

Thinking about it more, the cards need 12V from both end so I don't think you need a 5V rail at all.
In fact a PCI-E slot doesn't provide 5V, only 12V and 3.3V.

The USB riser might feed itself from the PCI-E lane (3.3V) and not the 5V from the molex. Not sure though.

Edit: tried a riser with the 5V rail on the molex disconnected and it didn't work. So the USB riser does require 5v.

Hmm! What a shame, I still have the same doubt, is it possible to feed the riser from the first PSU and leaves the second PSU to the GPUs?

If somebody knows the answer, I will really appreciate it.

[Alehandros]

I have 2x PSU (1000w and 1200w) with:
3x R9 Nano
2X R390x
1X HD7990

the 390x and HD are power hungry so one of the Nano's shares the riser power (to the 1200w) and the card power (to the 1000w) without any problems.

TL;DR: Mixing riser power and card power between PSUs seems to work for me

[jstefanop]

Whatever you do DONT EVER mix rails on different PSUs to the same load source. Even a slight voltage difference on the two PSUs will reek havoc on them, and will either fry your PSU, your GPU or cause your cabled to combust.

[Alehandros]

Whatever you do DONT EVER mix rails on different PSUs to the same load source. Even a slight voltage difference on the two PSUs will reek havoc on them, and will either fry your PSU, your GPU or cause your cabled to combust.

as in, don't power your riser and gfx cards from different sources?

[Narosya]

You can only supply the USB powered risers from the main PSU as that PSU supply power to the PCIE slot.

The pcie power socket on top of the card can be supplied by either the main or the secondary PSU.

[Alehandros]

You can only supply the USB powered risers from the main PSU as that PSU supply power to the PCIE slot.

The pcie power socket on top of the card can be supplied by either the main or the secondary PSU.

Hmm perhaps your wording is unclear.

I'm powering my riser and card from different power sources without problems, but does this practice risk my hardware?

thanks

[Narosya]

You can only supply the USB powered risers from the main PSU as that PSU supply power to the PCIE slot.

The pcie power socket on top of the card can be supplied by either the main or the secondary PSU.

Hmm perhaps your wording is unclear.

I'm powering my riser and card from different power sources without problems, but does this practice risk my hardware?

thanks

The riser can only be supplied from the main PSU.

The PCIE power connectors can be supplied from one of the main and secondary PSU. You cannot mix with one plug from main and one plug from secondary.

[philipma1957]

Hi there!

I'm building a mining rig (wheter it's profitable or not), my specs are:

Z77A-GD55 (Mainboard), Core i3-2100 (CPU), Corsair Vengeance 8GB (RAM), 500GB Sata (HDD), and now the problem:

I have a generic "500 Watts" (PSU), with this one, I'm pretending to supply the mainboard and HDD.

So far, the CPU works, it turns on and everything is working as expected.

The problem is... that 1st PSU won't be able to supply the 3 GPU I have (PowerColor R9 280x, Sapphire 7970, Gigabyte 7970).

So, AFAIK, I can supply those GPU with a different PSU in the 12V PCI connectors. So I buy this PSU ---> HP DPS-1200FB.

I asked before about turning on the GPU's PSU and then the mainboard PSU and there's no problem. In fact I can use a little relay to turn them both at the same time.

So yes, so far everything is OK.

But now another problem appears.

I'm using 3 of this usb risers, and now I'm not 100% sure of how should I supply them.

Some people says I must supply the usb risers with the 5v and 12v and both grounds (I mean 1 molex) from the mainboard PSU, and then only use the HP Server PSU to supply the PCI-6 and PCI-8 ports of the GPUs.

Some other people says I must get 5v and one ground from the generic PSU and 12v and the second ground from the HP PSU... to supply the mentioned risers.

I don't really know what to do, I'm afraid of damaging my GPU's. Is there anybody with experience here that can help me out?

Thanks in advance.

Stupid cheap bro = pennywise pound foolish

You are being guilty of the above.  your cards are worth close to 600 usd

here is a   set of links for you


http://www.ebay.com/sch/shopfsp/m.html?_nkw=&_armrs=1&_ipg=&_from=

http://www.ebay.com/itm/FSP-AURUM-PRO-80PLUS-GOLD-1200W-ModularCables-ATX12V-EPS-12V-Power-Supply-/182092039386?




This seller is the  actual manufacture  of the gear.

that 1200 watt psu  is a crazy good deal.

look at its price on amazon


http://www.amazon.com/FSP-Certified-Modular-Compatible-AU-1200PRO/dp/B007P8DKC0/ref=sr_1_1?ie=UTF8&qid=1460811184&sr=8-1&keywords=aurum+1200


it will run 3 cards up to 3 r9 390's

[baykan]

Hi,

I have a 1500 Watt PSU
4 gpus (R9 290s), one of them is connected to PCI-e 16x slot with a x1 to x1 unpowered extender. So it's connected x1. Others are connected with molex powered usb risers.

This is what happens :

Case 1
When 1 gpu is connected to PCI-e x16 slot via a x1 to x1 extender. Other gpus are disconnected. System hashing. No problem.

Case 2
When 2 or more gpus are connected, 1 of the gpus connected to PCI-e x16 slot via a x1 to x1 extender, and the other(s) via usb powered risers. Whenever the system starts hashing, computer freezes. All are powered from a single 1500 watt psu.

Case 3
Different thing from Case 2 is, Mainboard, HDD, all usb risers and the one gpu (pci-e 16x slot one) are connected to another 750 watt psu. Other gpus' 6 pin and 8 pins are connected to 1500 watt psu. system does not freeze.

My question is, when I replace the x1 to x1 unpowered extender with a powered usb riser, will I be able to power all with 1500 watt psu or not ?

I will try today or tomorrow anyway?

just wanted to share my question eating my brain for two days.
Thanks

[chup]

The riser can only be supplied from the main PSU.

The PCIE power connectors can be supplied from one of the main and secondary PSU. You cannot mix with one plug from main and one plug from secondary.

AFAIK power lines of powered risers are DISCONNECTED from mainboard, but You'll never know are they connected with power lines of GPU pcie power connectors inside GPU. Therefore, I'll bet on safe power supply when using SAME PSU on BOTH SIDES OF GPU (powered riser and pcie connectors).

[baykan]

To make my problem/question simpler.

I power 4 gpu's (6 pin and 8 pin connectors), motherboard+cpu with a 1500 watt psu.
One of the 4 gpus is connected via a flat unpowered riser, other 3 gpus are connected with usb powered risers.
I power 3 usb risers and the hdd with another 650 watt psu.
This setup is working just fine.

But I burned a hdd. How I burned it is :
Just powered the hdd with the 1500 watt psu.

What I'm doing wrong here ?
Is it a grounding problem that I can not figure out ?

Thanks in advance, for any answers.

[bathrobehero]

To make my problem/question simpler.

I power 4 gpu's (6 pin and 8 pin connectors), motherboard+cpu with a 1500 watt psu.
One of the 4 gpus is connected via a flat unpowered riser, other 3 gpus are connected with usb powered risers.
I power 3 usb risers and the hdd with another 650 watt psu.
This setup is working just fine.

But I burned a hdd. How I burned it is :
Just powered the hdd with the 1500 watt psu.

What I'm doing wrong here ?
Is it a grounding problem that I can not figure out ?

Thanks in advance, for any answers.

I'm not sure but I'd stay the away from flat unpowered risers. Powered USB risers are great and not expensive anymore.

[baykan]

To make my problem/question simpler.

I power 4 gpu's (6 pin and 8 pin connectors), motherboard+cpu with a 1500 watt psu.
One of the 4 gpus is connected via a flat unpowered riser, other 3 gpus are connected with usb powered risers.
I power 3 usb risers and the hdd with another 650 watt psu.
This setup is working just fine.

But I burned a hdd. How I burned it is :
Just powered the hdd with the 1500 watt psu.

What I'm doing wrong here ?
Is it a grounding problem that I can not figure out ?

Thanks in advance, for any answers.

I'm not sure but I'd stay the away from flat unpowered risers. Powered USB risers are great and not expensive anymore.

OK. I really appreciate your answer.
Any other ideas?

[mjgraham]

While you may have an answer when I did this kind of thing years ago the main thing it to make sure the grounds of all the supplies are connected, While I took  a much more advanced approach , like soldering connectors to the GPUs so I could get rid of the molex stuff I had a normal ATX supply for the PC and external supplies for the GPUs , you will need to be able to power cycle them and they need to come on at the same time if not the GPUs a split second earlier. The only time I had a problem was with a PCIe riser cable that I built my self that killed the motherboard but I had built the connector backwards. I have a link to some photos that I took back then, now if I was going to do this I would use the DPS-1200FB power supplies , pretty cheap for 100A I use them on my A2 miners, of course I have heavily modified them as well. Like that has been mentioned , most externals don't have a 5v rail, on my risers I just peeled the 12v off from the motherboard and let it do the rest, connect the grounds should be OK, as with most things do at your own risk.

http://photos.mag-productions.com/Hobbies/Altcoin/n-pFBSGx/

[Bazelak]

I have a few USB powered risers. I tested it. The +12V is not taken from the motherboard, it is only from the SATA +12 connector. So you can connect it to either main or the secondary PSU.