MP 7,1 Adding a second GPU for Windows 11

[SDAVE]

So I have a 6900XT and would like to add a 4090 just for Windows. I have dual Studio Displays connecteed via the Belink USBC > DisplayPort cable.

Is there dual monitor DisplayPort switch I can use to switch between the 4090 and 6900XT when I boot into Windows? It has to support 5k of course and be a single unit. I see some on Amazon but not sure if they'll work.

Cheers

 

[bax2023]

I don't know how you are going to power it. 7,1 has 4x 8-pin and 1x 6-pin power connectors.
6900 XT uses two of the 8-pins, and 4090 requires 3 or even 4 8-pin connectors.

After connecting 3rd party 6900 XT you are left with 2x 8-pins and 1x 6-pin and 4090 requires at least 3x 8-pins.

 

[SDAVE]

I don't know how you are going to power it. 7,1 has 4x 8-pin and 1x 6-pin power connectors.
6900 XT uses two of the 8-pins, and 4090 requires 3 or even 4 8-pin connectors.

After connecting 3rd party 6900 XT you are left with 2x 8-pins and 1x 6-pin and 4090 requires at least 3x 8-pins.

Is there some kind of splitter? The PSU on the 7,1 is 1000w i think?

 

[bax2023]

Its not a problem to make or buy a power splitter, but you can damage the traces on the logic board by connecting devices which draw more power then connectors and electronics are design to provide. You can also experience instability or Mac can refuse to boot. That is my advice. You can use external power supply to do that, if you don't mind cable mess.

Or, use less power hungry Radeon 6600(XT) together with 4090.

 

[d0sed0se]

This guy on reddit is using a 4090FE with the Belkin kit and he says it works well. Looks like he also has a W5700 MPX module in his 7,1.

SOURCE



There is also this other guy running 2x 4000 series cards in his 7,1

SOURCE

 

[bax2023]

Factory W5700 MPX does not use AUX power connectors from the motherboard, that is whay he had enough 8-pin power connectors for the GeForce. 3rd Party 6900 XT + GeForce 4090 would both have to use AUX power connectors.

 

[d0sed0se]

Factory W5700 MPX does not use AUX power connectors from the motherboard, that is whay he had enough 8-pin power connectors for the GeForce. 3rd Party 6900 XT + GeForce 4090 would both have to use AUX power connectors.

Since you ignored it -- Explain the second image/link then?

 

[bax2023]

Since you ignored it -- Explain the second image/link then?

I didn't ignore it, and you can calm down with your attitude toward someone who wants to help you.

I have explained it already, you can, as guy from the photo have done - install Y cables and get extra 8-pin or 6-pin power connectors - if you want to risk your few thousand dollars Mac.

Needed power is very easy to calculate:

Standard max PCIe power delivery - 75W.
6-pin - 75W
8-pin - 150W

If GPU requires 3x 8PIN connectors it means that it needs:
(75W) + 150W + 150W + 150W of power at max. Its crazy to deliver that via 1 or 2 connectors and just use splitter cables. Multiple users of MP5,1 here for example experienced instability and issues using 6-pin to 8-pin adapters. It coused reboots and instability, let alone to use one 8-pin and split it to 2x 8-pin.

That's it, I gave you friendly warning. Over and out.

 

[SDAVE]

This guy on reddit is using a 4090FE with the Belkin kit and he says it works well. Looks like he also has a W5700 MPX module in his 7,1.

SOURCE



There is also this other guy running 2x 4000 series cards in his 7,1

SOURCE

Cheers for this, that's good to know. Definitely want a 4090 or 5090 when that comes out. I have the W580X so I took that out.

I will look into the W5700X (which I think is underpowered) or maybe a used W6000 series MPX module.

But it's surprising that we can't split the power AUX since the PSU on the Mac Pro is very powerful already.

 

[Lihp8270]

Cheers for this, that's good to know. Definitely want a 4090 or 5090 when that comes out. I have the W580X so I took that out.

I will look into the W5700X (which I think is underpowered) or maybe a used W6000 series MPX module.

But it's surprising that we can't split the power AUX since the PSU on the Mac Pro is very powerful already.

But how much power can a single connector take when you start splitting them?