[SOLVED] Using be quiet! two Rail PSU with two different GPU with different power.

[Soprommat]

Hi folks.

I have be quiet Straight Power Gold 750W PSU.
https://www.bequiet.com/en/powersupply/1254

My PSU has two rails and three PCIe connectors. PCIe1 and PCIe3 are single rail connectors for rails 12V3 and 12V4 respectively. Also my PSu has PCIe2 connector which is connected to both rails and can provide more power.

Spoiler: Connector Image from manual

I want to use two graphic cards with different power. One power hundry card with power around 310 W with two x8 connectors. And one low power GPU with power around 105-125W and one x6 or x8 connector.

Based on avaliable info I have two constraints.

First.
Manual states that i must balance load across rails.

Spoiler: paragraph from manual

Second.
This video states that powerfull GPU must be plugged to PCIe2 connector.

View: https://www.youtube.com/watch?v=4GTOcemqb1Q



Does i understand correct: in my case I plug 310W card to PCIe2 and 125W card either to PCIe1 or PCIe3. In this case I have some small unballance across rails but it will be less than 125W because small video card will draw some power from PCIe x16 slot (google say that PCIe x16 is capable to transfer up to 75W but i dont know does PCIe x16 draw power first and remaining power taken from cable).

The other option is to connect one branch of PCIe1 and PCIe3 slots to powerfull card (im many similar topics users say that this method can reduce current losses a little bit) and connect my low hower video card to central powerfull PCIe2 slot. At first look now my rails are balanced.

What method is preferable or difference is neglectable?

Thanks in advance!

 

[USAFRet]

I want to use two graphic cards with different power.

The obvious first question is...Why 2x different GPU?

 

[Soprommat]

Powerful GPU for games and low power GPU is professional GPU like Quadro P4000 or AMD Radeon Pro WX 5500 for work.

 

[GoboII]

Powerful GPU for games and low power GPU is professional GPU like Quadro P4000 or AMD Radeon Pro WX 5500 for work.

Unless there's a specific feature you need from a workstation GPU, like 10-bit color or certified drivers, you are likely better off just using the faster GPU for both.

 

[Vic 40]

What cpu and motherboard? You might think this is of no importance, but with the lay out of that psu might it make a difference especially if the motherboard's cpu power connector needs more than one 8pin. Whether that is necessary is another question.

The 8pin cpu connector (EPS) and the 4+4pin connector do they come from on connector on the psu side? From the pictures i guess not, but would like to know.

 

[Soprommat]

GoboII

Workstation GPU perform much better in my working software (displaying CAD geometry) compared to gaming GPU, even if gaming GPU is more powerfull. As mentioned in softeare manual - software developers recieve a lot of help from Nvidia/AMD with professional video cards and recieve no help with gaming videocards.


Vic 40

My CPU is i7-11700 and mobo ASUS Tuf Gaming H570-Pro. Motherboard has one 1 x 8-pin +12V Power connector and PSU has separate rail (12V2) for 8-pin or 4+4-pin conector.

 

[Soprommat]

UPD. PSU has two 8-pin or 4+4-pin connectors.

 

[Vic 40]

First.
Manual states that i must balance load across rails.

Spoiler: paragraph from manual

The other option is to connect one branch of PCIe1 and PCIe3 slots to powerfull card (im many similar topics users say that this method can reduce current losses a little bit) and connect my low hower video card to central powerfull PCIe2 slot.

Would connect this way myself. From what is see the psu comes with two single 8pin cables and one cable with two connectors, would use the two single 8pin cables for the high power gpu and the other for the second gpu.

 

[Soprommat]

Thank you .

 

[Vic 40]

You're welcome.