# [SOLVED]Powering 4 GPUs from single PSU ?

#### MEIZ

Hey! I need your help, guys.
I am trying to setting up a rig and have some questions.
I have researched around, but many answers are too old and I do not know what is relevant and what is not to daily standards.

I currently have:
PSU: Cooler Master 850V Gold SFX (4 PSI-e slots)
GPU: 1x GTX 1080, 3x GTX 1070
Risers: ver009/010

So problem is right now is to power all of these.
I currently run 1x 1080 and 1x 1070 with from 2 PCI-e slots of PSU. I also power 2 risers of single SATA. I experience no issues so far, cables are cool, everything is fine. 1080 consumes around 150W tops of dual 8 pin cable and 1070 is consuming 135W tops of single 8 pin.

So current power usage is around 150 + 135 + 100(system) = 385W of 680W(850W *0.8) available.

I have 2 more 1070 coming soon and wondering how I should arrange power. I have 2 PCI-e slots used by current 2 cards, 1 slot used by CPU and 1 slot free.
Correct me if I am wrong, but my PSU can supply 288W off single PCI-e slot, so technically connecting 2 new 1070 to a single PCI-e slot with Y splitter should work? Since they do not consume as much.

With two more 1070 my power consumption should spike to 385W(current) +170W(2x1070s) = 555W of 680W. That should be plenty for those 4 cards.

How do I solve this puzzle? I appreciate all help and knowledge.

Last edited:

#### kerberos_20

##### Illustrious
hmm actually you should count energy requirement at max pcie spec capacity, as power can spike above its normal level in short bursts...which means gpu running at 250watts can spike to 300watts without you knowing (unless you check that with oscilometer)
pcie spec wattage for 1070/ 1080 is as follow:
pcie slot = 75watts (it powers up GPU VRAM)
1x 8pin = 150watts (it powers up GPU die)
1x 6pin = 75watts (additional power for extra overclock not all boards have it)

so a 1080 would be 150+150 +75 = 375watts (2x8pin+pcie slot)
and a non OC 1070 would be 150+75 = 225watts

375+225+225+225 = well youre on 1050watts on just GPUs
keep in mind that this is max capacity for GPU so PSU wont shutdown with OCP protection (gpu load in ~80% of this with spikes up to this number]
now add some watts for rest of your PC...USB ~50watts, ram ~50watts, mainboard 10watts, any extra pcie device (75watt each),some drives and CPU
so maybe 250watts here

https://www.amazon.com/Seasonic-Platinum-SSR-1300PD-Modular-Warranty/dp/B0788DL6VN?th=1

#### kerberos_20

##### Illustrious
hmm actually you should count energy requirement at max pcie spec capacity, as power can spike above its normal level in short bursts...which means gpu running at 250watts can spike to 300watts without you knowing (unless you check that with oscilometer)
pcie spec wattage for 1070/ 1080 is as follow:
pcie slot = 75watts (it powers up GPU VRAM)
1x 8pin = 150watts (it powers up GPU die)
1x 6pin = 75watts (additional power for extra overclock not all boards have it)

so a 1080 would be 150+150 +75 = 375watts (2x8pin+pcie slot)
and a non OC 1070 would be 150+75 = 225watts

375+225+225+225 = well youre on 1050watts on just GPUs
keep in mind that this is max capacity for GPU so PSU wont shutdown with OCP protection (gpu load in ~80% of this with spikes up to this number]
now add some watts for rest of your PC...USB ~50watts, ram ~50watts, mainboard 10watts, any extra pcie device (75watt each),some drives and CPU
so maybe 250watts here

https://www.amazon.com/Seasonic-Platinum-SSR-1300PD-Modular-Warranty/dp/B0788DL6VN?th=1

#### Archaic59

##### Polypheme
Hey! I need your help, guys.
I am trying to setting up a rig and have some questions.
I have researched around, but many answers are too old and I do not know what is relevant and what is not to daily standards.

I currently have:
PSU: Cooler Master 850V Gold SFX (4 PSI-e slots)
GPU: 1x GTX 1080, 3x GTX 1070
Risers: ver009/010

So problem is right now is to power all of these.
I currently run 1x 1080 and 1x 1070 with from 2 PCI-e slots of PSU. I also power 2 risers of single SATA. I experience no issues so far, cables are cool, everything is fine. 1080 consumes around 150W tops of dual 8 pin cable and 1070 is consuming 135W tops of single 8 pin.

So current power usage is around 150 + 135 + 100(system) = 385W of 680W(850W *0.8) available.

I have 2 more 1070 coming soon and wondering how I should arrange power. I have 2 PCI-e slots used by current 2 cards, 1 slot used by CPU and 1 slot free.
Correct me if I am wrong, but my PSU can supply 288W off single PCI-e slot, so technically connecting 2 new 1070 to a single PCI-e slot with Y splitter should work? Since they do not consume as much.

With two more 1070 my power consumption should spike to 385W(current) +170W(2x1070s) = 555W of 680W. That should be plenty for those 4 cards.

How do I solve this puzzle? I appreciate all help and knowledge.
So current power usage is around 150 + 135 + 100(system) = 385W of 680W(850W *0.8) available.
Uh...no. This is not how efficiency rating works. You don't lose capacity. An 850 watt PSU that can deliver full power at 80% efficiency will draw around 1020 watts from the wall outlet to get the 850. ie... 850 x 1.20 = 1020 watts. At 90% efficiency it will draw 935 watts from the wall outlet to get the 850. ie... 850 x 1.10 = 935 watts

#### DRagor

##### Illustrious
With two more 1070 my power consumption should spike to 385W(current) +170W(2x1070s) = 555W of 680W. That should be plenty for those 4 cards.
Should be 385 + 270 = 655
In any case connecting two cards to just one PCIe slot is not recommended. I'd say your current setup has room for one more card safely. Add two and expect trouble sooner or later.

#### MJS WARLORD

##### Honorable
Just curious , why do you want or need 4 graphics cards ?
A few people have told you it is probably not a good idea , however , if you are determined to go ahead and do it anyway i would suggest that you either email nvidea support or your cards individual maker for advice on the best way to do it !

I got the zotac version of the gtx1080 put into a custom built rig when it first came out. You dont need to use the overclocking program on the driver disc , i contacted zotac as i was not sure how to use the overclocking program and they said the card has the ability to overclock itself if it ever gets put under extreme load.
If that is correct then why bother putting the program on the disc in the first place ?

#### arif1752002m4a1

##### Reputable
When we talk about real world scene... GPUs also draws power in surges.. like Msi GTX 1080ti Gaming X sometimes draws 370 watts for 0.5 Seconds... (I have tested using 0.75mv shunt and a sketchy diy oscilloscope... ) And if we add this peak power draw for every card.. i will say GTX 1080Ti 5 and GTX 10701... I will use 2.3KW PSU for reliable system operation... And as far as my electronic knowledge goes . If we are dealing with that Much power.. specially more than 750 Watts. We should use multiple PSUs or multi rail 12v PSUs.. to prevent Explosions.. in worse cases...

Like if you used 2KW PSU for your RIG... And one of the card just shorted to ground.. means for an instant.. 2.6KW (PSUs are Tested and set to trip for 130% overload) will flow from one card from one of VRM phase.. That card will catch fire instantly...

If you use multiple rail PSU . With every rail set for 400 watt Trip power... If any card shorts.. only 400 watt for an instant will be required to switch PSU off... Without blowing anything...
So i will say use multiple Rail PSU..

Or i will say use 3*1KW Multirail PSUs... To make your RIG Stable and safe..(it will not as stable as 1 PSU one if you don't build it perfectly)..

Safety should be Top priority guys...

#### kerberos_20

##### Illustrious
When we talk about real world scene... GPUs also draws power in surges.. like Msi GTX 1080ti Gaming X sometimes draws 370 watts for 0.5 Seconds... (I have tested using 0.75mv shunt and a sketchy diy oscilloscope... ) And if we add this peak power draw for every card.. i will say GTX 1080Ti 5 and GTX 10701... I will use 2.3KW PSU for reliable system operation... And as far as my electronic knowledge goes . If we are dealing with that Much power.. specially more than 750 Watts. We should use multiple PSUs or multi rail 12v PSUs.. to prevent Explosions.. in worse cases...

Like if you used 2KW PSU for your RIG... And one of the card just shorted to ground.. means for an instant.. 2.6KW (PSUs are Tested and set to trip for 130% overload) will flow from one card from one of VRM phase.. That card will catch fire instantly...

If you use multiple rail PSU . With every rail set for 400 watt Trip power... If any card shorts.. only 400 watt for an instant will be required to switch PSU off... Without blowing anything...
So i will say use multiple Rail PSU..

Or i will say use 3*1KW Multirail PSUs... To make your RIG Stable and safe..(it will not as stable as 1 PSU one if you don't build it perfectly)..

Safety should be Top priority guys...
1080ti is rated for 375watts max, he doesn't have 2x 8pin GPU

#### MEIZ

I have now upgraded PSU to one that have one more PCIE slot, that makes 1 slot for CPU and 4 for GPU cards. I can therefore use 1 slot for each card, which should remove risk associated with connecting 2 GPUs to one PCIE slot.

Should be 385 + 270 = 655
In any case connecting two cards to just one PCIe slot is not recommended. I'd say your current setup has room for one more card safely. Add two and expect trouble sooner or later.
Yeah, combination of a typo and bad math You're right. around 655W. Now with one extra slot I can delegate each card with a safe connection and Wattage should be enough and safely distributed.