FS: PCI-Express Extender Cables(w/ Molex)*GPU Dummy Plugs*PSU Adapters

[1bitc0inplz]

This looks like a good idea.

I am bookmarking this, as it looks like a good upgrade when I'm ready to add a second mining GPU.

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[Inaba]

I got my order of extenders today.  However, I have a question/concern.  I'm not terribly knowledgeable about the PCIe pin package, so forgive me... but only the +12v connection on the PCIe bus is connected to these via the MOLEX.  That would seem to me it's allowing the ground to go through the bus on the motherboard.

If I were to power one of my cards with a PSU that is NOT powering the motherboard, it's going to create a ground differential that may burn out the card, the motherboard or both.  Can someone explain why this is not an issue?  Or are the cards taking their 75v from the PCIe bus not grounded through the bus?  I'm thinking they have to be, since you can put cards in a machine that do not have external power requirements and supply solely off of the bus. 

[trentzb]

This may be an issue although I cannot definitively confirm as I haven't modified PCIe extenders to peel off the 12V to test yet....will do so in coming days.

However I did work on multiple PSU arrangements yesterday where one is powering board/peripherals and a GPU or two and a secondary ATX PSU powers additional GPUs. This arrangement works but grounds must be connected between PSUs. It may be something specific to my particular PSUs but I found it was not enough to light up a GPU by just making PSU #2 hot with PSON. I had to connect PSON + GND to PSU #1 and I was then able to light up additional GPUs.

I also wonder about how a GPU will light up if PCIe +12 but not GND is supplied from a secondary PSU/source. I believe forum user mrb has experience in this area, maybe he can provide some insight if he runs across this thread.

[Cablesaurus]

Ground is going through the PCIe bus. Pins A2+A3;B1+B2+B3 are the 12v pins rewired to the Molex. Regarding GPU detection using these cables on a 5970 or 6990 would detect without further wiring modifications.

Trentbz/Inaba, http://blog.zorinaq.com/?e=44 Per the reference posted in this blog and confirmed test current drops from a combined 14A to < 1A. Preventing cable wear from extended use. Let me know if any questions.

[Inaba]

Ground is going through the PCIe bus. Pins A2+A3;B1+B2+B3 are the 12v pins rewired to the Molex. Regarding GPU detection using these cables on a 5970 or 6990 would detect without further wiring modifications.

Trentbz/Inaba, http://blog.zorinaq.com/?e=44 Per the reference posted in this blog and confirmed test current drops from a combined 14A to < 1A. Preventing cable wear from extended use. Let me know if any questions.

Thanks for the link, but I don't see where it's saying he was using two power supplies with independent ground potential.  From the way the blog reads, he's connecting the +12v to the same PSU that is supplying power to the motherboard, making the ground the same regardless of the +12v source.

If my +12v source is coming from a different PSU than is grounding the motherboard, the potential will be different and that's where the bad things can start.  I completely agree that there would be no problem supplying +12v from a molex on the same PSU that's grounding the motherboard.

[trentzb]

I believe mrb is using dual PSUs as listed at http://blog.zorinaq.com/?e=42.

First PSU to power the four 8-pin connectors:
4 * 11.4 (8-pin) = 45.6 Amp
Second PSU to power everything else (four 6-pin connectors + four cards via PCIe slot + ATX connectors for mobo/CPU):
4 * 6.7 (6-pin) + 4 * 3.7 (slot) + ~3 (mobo/CPU) = ~45 Amp

I can't determine by his post how he has ground connected between them except that supplying the PCIe 8-pin via PSU #1 and supplying the PCIe 6-pin + PCIe slot via PSU #2 should tie them together sufficiently...not sure if this was intentional or not though.

I am not yet providing 12V to the PCIe slot via an extender but I did do dual PSUs yesterday and when I supplied PCIe 6-pin from PSU #2 to GPUs and PCIe slot/ATX/peripherals via PSU #1 I could not get GPUs to light up. As soon as I cross connected the PSUs via PSON and GND the GPUs lit up as expected.

I would suspect that you may have issues if you provide PCIe 12V and/or PCIe 6/8-pin from a secondary PSU that is NOT common ground with primary PSU. I know I did with providing PCIe 6-pin separate than PCIe slot 12V.

And fortunately, I didn't kill any GPUs during my 30 second power up.

[marcus_of_augustus]

Ground is going through the PCIe bus. Pins A2+A3;B1+B2+B3 are the 12v pins rewired to the Molex. Regarding GPU detection using these cables on a 5970 or 6990 would detect without further wiring modifications.

Trentbz/Inaba, http://blog.zorinaq.com/?e=44 Per the reference posted in this blog and confirmed test current drops from a combined 14A to < 1A. Preventing cable wear from extended use. Let me know if any questions.

Thanks for the link, but I don't see where it's saying he was using two power supplies with independent ground potential.  From the way the blog reads, he's connecting the +12v to the same PSU that is supplying power to the motherboard, making the ground the same regardless of the +12v source.

If my +12v source is coming from a different PSU than is grounding the motherboard, the potential will be different and that's where the bad things can start.  I completely agree that there would be no problem supplying +12v from a molex on the same PSU that's grounding the motherboard.

Yes, best if used off the same PSU. Also if using multiple PSUs just make sure all your grounds are common. What crazy set-up would have two PSU's right next too each other, supplying the same equipment with 'floating' grounds? You are asking for trouble if that is your case anyway.

Whole server farms make sure that the ground is common throughout the building. If you want to have floating grounds that is your own problem I'd say. The basic idea is to bypass power around mobo to PCIe GPU card, ATX PSU connectors have reported burnouts with more than 3 5970's on same mobo.

[dishwara]

Ground is going through the PCIe bus. Pins A2+A3;B1+B2+B3 are the 12v pins rewired to the Molex. Regarding GPU detection using these cables on a 5970 or 6990 would detect without further wiring modifications.

Trentbz/Inaba, http://blog.zorinaq.com/?e=44 Per the reference posted in this blog and confirmed test current drops from a combined 14A to < 1A. Preventing cable wear from extended use. Let me know if any questions.

Thanks for the link, but I don't see where it's saying he was using two power supplies with independent ground potential.  From the way the blog reads, he's connecting the +12v to the same PSU that is supplying power to the motherboard, making the ground the same regardless of the +12v source.

If my +12v source is coming from a different PSU than is grounding the motherboard, the potential will be different and that's where the bad things can start.  I completely agree that there would be no problem supplying +12v from a molex on the same PSU that's grounding the motherboard.

Yes, best if used off the same PSU. Also if using multiple PSUs just make sure all your grounds are common. What crazy set-up would have two PSU's right next too each other, supplying the same equipment with 'floating' grounds? You are asking for trouble if that is your case anyway.

Whole server farms make sure that the ground is common throughout the building. If you want to have floating grounds that is your own problem I'd say. The basic idea is to bypass power around mobo to PCIe GPU card, ATX PSU connectors have reported burnouts with more than 3 5970's on same mobo.

"all your grounds are come"  what does it exactly mean?

In my house their is a ground given by inserting a 1 inch GI pipe in to earth for around 2 feet & a wire is connected to that, that wires goes to every electrical  board in my house & connect to central big connector in a 3 pin connector.
Is that you saying to have common ground?

Today, i have to run 2 systems with one pc has one 6870 & other has one 5870.
I have only one cooler master GX 550W power supply & 2 low cost PSU which comes with cabinets.
I thought of connecting the low cost psu to motherboard & give power to system.
Then short the pin of GX 550 W PSU mother board connector 20 + 4 pin (Don't know which 2 pins/connections to short), which will switch on the GX 550 W PSU.
& then connecting(only after switching off 550 W PSU & computer) PCI-e 6 pins connectors from GX 550W PSU to the cards in 2 separate pc, the 6870 & 5870.

Can it be done & is it safe to do it?
I won't run this setup for months. It is just for 3-7 days, until i get Cooler master silent pro gold 1200 W. Its in shipment & i don't want my newly bought 5870 card lying around.

[marcus_of_augustus]

just make sure all your grounds are common

that's what I said .... read slower maybe?

[dishwara]

I understand you saying common ground.
I am asking, is my above setup will be safe?, coz besides ground, it may rise some other problem, that why asking.

[Inaba]

Aren't the PSU's and/or motherboards floating ground by design?  I just don't know enough about the internal grounding of a computer PSU and the motherboards to speak with any authority which is why I was asking.  But I thought I remember reading somewhere that most commodity hardware on the desktop has floating grounds due to cost issues or something?

[nelisky]

Would you also be able to provide the cable to power up 2 PSUs in tandem? Something like http://www.frozencpu.com/products/11742/cpa-167a/ModRight_CableRight_Dual_Power_Supply_Adapter_Cable.html?tl=g2c413s1220&id=qNzMZhNn

[dishwara]

Would you also be able to provide the cable to power up 2 PSUs in tandem? Something like http://www.frozencpu.com/products/11742/cpa-167a/ModRight_CableRight_Dual_Power_Supply_Adapter_Cable.html?tl=g2c413s1220&id=qNzMZhNn

You can go for that cable, which is hassle free. But yesterday, i have to run my 5870 card, so used the psu(220-250W) in cabinet as it is. Then took another 250 W PSU, using molex to pcie 6 pin connector, connected & powered the 5870 card.
To start PSU, i used a wire to short pin 14 & ground. Pin 14 is GREEN & ground/com is any black which is near.
Everything works fine.
You can try this simple method & for safety use cello tape to cover the wire & 20/24 pin motherboard connector, which avoids accidental pulling of wire & safe to handle.
Or you can buy that cable. I hope technopagan can buy & send for you, but the shipping cost & time will be a problem if you are far from him.

This pages help to make it on your own.
http://pinouts.ru/Power/atxpower_pinout.shtml
http://aphnetworks.com/lounge/turn_on_psu_without_motherboard_the_paperclip_trick

This last one uses a switch, instead of wire, which help you to switch on & off.
http://www.gideontech.com/content/articles/196/1

[nelisky]

You can go for that cable, which is hassle free. But yesterday, i have to run my 5870 card, so used the psu(220-250W) in cabinet as it is. Then took another 250 W PSU, using molex to pcie 6 pin connector, connected & powered the 5870 card.
To start PSU, i used a wire to short pin 14 & ground. Pin 14 is GREEN & ground/com is any black which is near.
Everything works fine.
You can try this simple method & for safety use cello tape to cover the wire & 20/24 pin motherboard connector, which avoids accidental pulling of wire & safe to handle.
Or you can buy that cable. I hope technopagan can buy & send for you, but the shipping cost & time will be a problem if you are far from him.

This pages help to make it on your own.
http://pinouts.ru/Power/atxpower_pinout.shtml
http://aphnetworks.com/lounge/turn_on_psu_without_motherboard_the_paperclip_trick

This last one uses a switch, instead of wire, which help you to switch on & off.
http://www.gideontech.com/content/articles/196/1

Thanks for that. I actually used the green/black wire trick many times on water cooled set ups to fill the system and remove air bubbles without booting anything up. I can use that, certainly, but I don't like the idea of someday having to power down the machine remotely (has happened) and having that PSU just running and feeding a GPU, thus I search for something more permanent. I could just hack the thing up, push some clips into the connectors and all but there's enough equipment value involved to go that extra step.

[dishwara]

Definitely, value of hardware is important. I gave the link for temporary purpose only, which i found out yesterday to run my pc & happy that you used that before itself.
The cable you mentioned, is actually the best solution available, coz it won't need additional on/off, watching....
 

[caston]

I assume you could use these cable mods to run your PCI'e cards from a different PSU to your system PSU?

[Cablesaurus]

I assume you could use these cable mods to run your PCI'e cards from a different PSU to your system PSU?

If you're using a PSU not grounded to the motherboard, do not utilize a cable with modification. Make sure any secondary PSU to be used would be grounded through the motherboard.

[Cdecker]

I assume you could use these cable mods to run your PCI'e cards from a different PSU to your system PSU?

If you're using a PSU not grounded to the motherboard, do not utilize a cable with modification. Make sure any secondary PSU to be used would be grounded through the motherboard.

How would you go about grounding the PSU to the motherboard? Is is enough to mount them in the same (conductive) case?

[nelisky]

I assume you could use these cable mods to run your PCI'e cards from a different PSU to your system PSU?

If you're using a PSU not grounded to the motherboard, do not utilize a cable with modification. Make sure any secondary PSU to be used would be grounded through the motherboard.

By using the mentioned "hack" we will be connecting one "COMMON" line along with the "PS_ON". This is ground(ed), right?

[Cablesaurus]

I assume you could use these cable mods to run your PCI'e cards from a different PSU to your system PSU?

If you're using a PSU not grounded to the motherboard, do not utilize a cable with modification. Make sure any secondary PSU to be used would be grounded through the motherboard.

How would you go about grounding the PSU to the motherboard? Is is enough to mount them in the same (conductive) case?

I'm not sure if grounding to the case would be sufficient, it may or may not. More input would be helpful.
I've not used 2-PSU setups on my rigs.