Connecting 6 GPUs to 2 PSUs, please, help...

spinx

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Activity: 139

Merit: 100

Quote from: Eastwind on February 11, 2014, 02:00:33 PM

Quote from: spinx on February 11, 2014, 12:52:04 PM

Quote from: Eastwind on February 10, 2014, 01:51:58 PM

Quote from: spinx on February 10, 2014, 11:00:18 AM

Quote

You have to connect ALL the riser molex to the main PSU.

# 1 - Corsair CX750
* Motherboard 100W
* 1 GPU = 1 * 75 = 75W
* 6 PCIE slot (4+2)*75W = 450W
* Fans 10W
(total = 100+75+450W +10W = 635W 85% of 750W)

# 2 - Fractal R2 750W
* 5 GPU = 5 * 75W = 375W
* (5x 6pin + 0molex)
(total about 50% of 750W)

Like this?

The only problem i have then is regarding PSU #2, the Fractal R2. It has 2 rails and limited connectors, im thinking like this:

Rail #1 - 30amp*12V=360W
1x pci-e (1*75W)
6x molex -> 3x pci-e 6pin (3*75W=225W)
= 300W for 4pcs 6pin

Rail #2 - 30amp*12V=360W
1x pci-e (1*75W) -> 2 x 6pin (will make this converter myself)
OR
1x EA12V -> 6pin?

Your picture is right indication of the set up.

For fractal R2, you can use the 4*6pin from Rail1 and one from the EA12V->6pin. I do not know the distribution of power between rails. I just assume Rail 1 is the 4*(6+2)pin+peripheral, and Rail 2 is the MB connector +CPU12V.

It is better to use two CTX750 if you have not bought the Fractal.

I have now purchased and installed a Corsair CX750 as the main PSU, everything connected as desribed above. But the damn 2nd PSU, Fractal R2 keeps shutting down on boot. Its only loaded with 4x 6pin pcie (4*75W=300W) so its not overloaded. Can the problem be that it needs some load on 5V aswell? I remember something like that from back in the days.

"Many PC PSUs (not all) require a base load on the 5V rail to work properly. Connecting an old CD drive or a 12V light bulb (into the 5V rail, see picture) are well proven methods to get this load."
http://reprap.org/wiki/PCPowerSupply

Discussed here https://bitcointalksearch.org/topic/light-bulb-5v-psu-load-how-much-is-enough-50178

When the system boots, it does not use much power, so it might not be unbalance of the rails. You can verify that by swapping the PSU. If it does not shut down on boot, then unbalance is the reason.

You also remove some cards from 2nd PSU, and add one after the other.

OMFG i finally got it to work by connecting an old DVD-rom to the molex on the 2nd PSU (Fractal), all to get som load on the 5V-line. Its now hashing with 6 GPU´s for 30min!

Eastwind

hero member

Activity: 896

Merit: 1000

Quote from: spinx on February 11, 2014, 12:52:04 PM

Quote from: Eastwind on February 10, 2014, 01:51:58 PM

Quote from: spinx on February 10, 2014, 11:00:18 AM

Quote

You have to connect ALL the riser molex to the main PSU.

# 1 - Corsair CX750
* Motherboard 100W
* 1 GPU = 1 * 75 = 75W
* 6 PCIE slot (4+2)*75W = 450W
* Fans 10W
(total = 100+75+450W +10W = 635W 85% of 750W)

# 2 - Fractal R2 750W
* 5 GPU = 5 * 75W = 375W
* (5x 6pin + 0molex)
(total about 50% of 750W)

Like this?

The only problem i have then is regarding PSU #2, the Fractal R2. It has 2 rails and limited connectors, im thinking like this:

Rail #1 - 30amp*12V=360W
1x pci-e (1*75W)
6x molex -> 3x pci-e 6pin (3*75W=225W)
= 300W for 4pcs 6pin

Rail #2 - 30amp*12V=360W
1x pci-e (1*75W) -> 2 x 6pin (will make this converter myself)
OR
1x EA12V -> 6pin?

Your picture is right indication of the set up.

For fractal R2, you can use the 4*6pin from Rail1 and one from the EA12V->6pin. I do not know the distribution of power between rails. I just assume Rail 1 is the 4*(6+2)pin+peripheral, and Rail 2 is the MB connector +CPU12V.

It is better to use two CTX750 if you have not bought the Fractal.

I have now purchased and installed a Corsair CX750 as the main PSU, everything connected as desribed above. But the damn 2nd PSU, Fractal R2 keeps shutting down on boot. Its only loaded with 4x 6pin pcie (4*75W=300W) so its not overloaded. Can the problem be that it needs some load on 5V aswell? I remember something like that from back in the days.

"Many PC PSUs (not all) require a base load on the 5V rail to work properly. Connecting an old CD drive or a 12V light bulb (into the 5V rail, see picture) are well proven methods to get this load."
http://reprap.org/wiki/PCPowerSupply

Discussed here https://bitcointalksearch.org/topic/light-bulb-5v-psu-load-how-much-is-enough-50178

When the system boots, it does not use much power, so it might not be unbalance of the rails. You can verify that by swapping the PSU. If it does not shut down on boot, then unbalance is the reason.

You also remove some cards from 2nd PSU, and add one after the other.

Eastwind

hero member

Activity: 896

Merit: 1000

Quote from: bananahunter67 on February 11, 2014, 12:23:25 PM

Any card and any riser. Card wont start up if directlyconnected to MB. It starts if connected via riser without molex. By "start" I mean fan starts spinning.

You can try a different kind of GFX card, if it does not work, then motherboard/memory, cpu might be faulty.

spinx

full member

Activity: 139

Merit: 100

Quote from: Eastwind on February 10, 2014, 01:51:58 PM

Quote from: spinx on February 10, 2014, 11:00:18 AM

Quote

You have to connect ALL the riser molex to the main PSU.

# 1 - Corsair CX750
* Motherboard 100W
* 1 GPU = 1 * 75 = 75W
* 6 PCIE slot (4+2)*75W = 450W
* Fans 10W
(total = 100+75+450W +10W = 635W 85% of 750W)

# 2 - Fractal R2 750W
* 5 GPU = 5 * 75W = 375W
* (5x 6pin + 0molex)
(total about 50% of 750W)

Like this?

The only problem i have then is regarding PSU #2, the Fractal R2. It has 2 rails and limited connectors, im thinking like this:

Rail #1 - 30amp*12V=360W
1x pci-e (1*75W)
6x molex -> 3x pci-e 6pin (3*75W=225W)
= 300W for 4pcs 6pin

Rail #2 - 30amp*12V=360W
1x pci-e (1*75W) -> 2 x 6pin (will make this converter myself)
OR
1x EA12V -> 6pin?

Your picture is right indication of the set up.

For fractal R2, you can use the 4*6pin from Rail1 and one from the EA12V->6pin. I do not know the distribution of power between rails. I just assume Rail 1 is the 4*(6+2)pin+peripheral, and Rail 2 is the MB connector +CPU12V.

It is better to use two CTX750 if you have not bought the Fractal.

I have now purchased and installed a Corsair CX750 as the main PSU, everything connected as desribed above. But the damn 2nd PSU, Fractal R2 keeps shutting down on boot. Its only loaded with 4x 6pin pcie (4*75W=300W) so its not overloaded. Can the problem be that it needs some load on 5V aswell? I remember something like that from back in the days.

"Many PC PSUs (not all) require a base load on the 5V rail to work properly. Connecting an old CD drive or a 12V light bulb (into the 5V rail, see picture) are well proven methods to get this load."
http://reprap.org/wiki/PCPowerSupply

Discussed here https://bitcointalksearch.org/topic/light-bulb-5v-psu-load-how-much-is-enough-50178

bananahunter67

sr. member

Activity: 392

Merit: 265

Any card and any riser. Card wont start up if directlyconnected to MB. It starts if connected via riser without molex. By "start" I mean fan starts spinning.

Eastwind

hero member

Activity: 896

Merit: 1000

When you say startup, does it mean the card has display? If so, card and PSU is working.

Does it happen to all the cards?

You can change the risers to see if it is faulty. If there is display with other risers, then the original one is not working.

bananahunter67

sr. member

Activity: 392

Merit: 265

Debug update: When the molex of the card is connected to the PSU, the card doesn't run.
Also the card doesnt run when directly connected to MB.
It startups only when connected with riser cable whose molex is not connected to PSU.
Any ideas on that?

Eastwind

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Activity: 896

Merit: 1000

Quote from: bananahunter67 on February 11, 2014, 07:18:30 AM

OK, I just did the test on the other rig, only 1 card, connected directly to MB slot, and with 6/8 to 1 PSU. Again, not starting. I think the chance both MB or cards not to be working is 0% so obviously should be some misconfiguration of the hardware... Roll Eyes

Try other cards.

Eastwind

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Activity: 896

Merit: 1000

Quote from: bananahunter67 on February 11, 2014, 07:14:02 AM

How shall I do this (the measurement)?

If you ask this question, I assume you have not used it before. So do not bother.

It is better to work from the beginning.

Disconnect all unnecessary parts. Just connect the MB, keyboard and mouse with memory, GFX card no hard disk. You need to connect the CPU +12V as well.

Power on the system to see if there is on screen display. Try with different monitor.

You can use the Fractal PSU as the main PSU as well.

bananahunter67

sr. member

Activity: 392

Merit: 265

OK, I just did the test on the other rig, only 1 card, connected directly to MB slot, and with 6/8 to 1 PSU. Again, not starting. I think the chance both MB or cards not to be working is 0% so obviously should be some misconfiguration of the hardware... Roll Eyes

bananahunter67

sr. member

Activity: 392

Merit: 265

How shall I do this (the measurement)?

Eastwind

hero member

Activity: 896

Merit: 1000

Do not use the 2nd PSU.

Try other cards.

If none of the cards are working, then the system (MB) is not working. Can you use a multmeter to measure the voltage output from the PSU? The 3.3V, 5V and 12V.

bananahunter67

sr. member

Activity: 392

Merit: 265

Edit: Hm, thats interesting, OK, I really gave it a try with the only one card connected directly to the MB without riser and the card doesn't start up! Shocked

What should that mean?

bananahunter67

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Activity: 392

Merit: 265

MB is working, however, I suspect that problem may be that I am using an old monitor with VGA to DVI-I adapter...

Eastwind

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Activity: 896

Merit: 1000

Quote from: bananahunter67 on February 11, 2014, 06:31:15 AM

OK, I unplugged all card except to one which is currently connected only to first PSU with 6/8, riser molex is unplugged. This time only this card started (it is different). I plugged the monitor into it, but still, black scree only.

Can you connect the card directly to the slot? We want to make sure the MB is working.

If you see the screen display, then use the riser with molex.

bananahunter67

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Activity: 392

Merit: 265

OK, I unplugged all card except to one which is currently connected only to first PSU with 6/8, riser molex is unplugged. This time only this card started (it is different). I plugged the monitor into it, but still, black scree only.

Eastwind

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Activity: 896

Merit: 1000

Quote from: bananahunter67 on February 11, 2014, 06:18:49 AM

Yes, exactly, only 2 of the 6 GPUs fan spins. And I exactly plug my monitor into one of them.

If the 2nd PSU fan spins, that means there is power out of it. So it is working.

Can you remove all the 5 cards from the 2nd PSU and add them one by one?

Can you also check if there is screen display when there is only one card connected to the main PSU?

bananahunter67

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Activity: 392

Merit: 265

Yes, exactly, only 2 of the 6 GPUs fan spin. And I exactly plug my monitor into one of them.
And yes, both PSU fan spin.
Also if this helps, the two cards which'w fan spins are the ones connected to the second PSU and with 1x/16x cables to the MB.

Eastwind

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Activity: 896

Merit: 1000

Does the GPU fan spin?
Does the 2nd PSU fan spin?

bananahunter67

sr. member

Activity: 392

Merit: 265

OK, so I connected finally everything, and started the motherboard and the 2 PSUs. The results is that only 2 of the 6 cards start up and while the monitor is plugged into one of them, it doesnt show nothing, just black screen. Anyone Huh

Topic: Connecting 6 GPUs to 2 PSUs, please, help... (Read 2211 times)