5995wx workstation with dual power supply units - second PSU doesn't start

[shumyeah]

I am building a workstation for a machine learning project with the following specs:

CPU: Threadripper 5995wx
Motherboard: ASUS Pro WS WRX80E
Memory: SAMSUNG 512GB
Storage: SSD 2 TB x1, SSD 8 TB x1
GPU: Geforce RTX 3090 TI 24 GB x4
Mining Rig
Power Supply: EVGA P2 1600 W 80+ Platinum, Corsair 1000 W 80+ Platinum
Linux Ubuntu 20.04
Noctua fans x6

My problem is, I am able to boot 1st and 2nd GPU connected to the main PSU, and log into Ubuntu. The 3rd and 4th GPU, connected to the second PSU, won’t start.

I tested both PSUs with a power supply tester and they both work. I then tried (i) dual power a 24pin dual power supply adapter; (ii) a 24pin power supply splitter; and (iii) a PSU jumper. Unfortunately none of those works.

I also tried to use 1 GPU for each PCI slot on the motherboard, and all 7 slots work.

Appreciate any comments/guidance on what went wrong and possible solutions to get the 3rd and 4th GPU to work together.

Thanks everyone!

[GigaBusterEXE]

can you upload a picture of the splitter you have

[shumyeah]

[GigaBusterEXE]

is the first picture the tester?

[shumyeah]

That’s an adapter called Add2PSU chip. Available on Amazon.

[GigaBusterEXE]

Have you tried using a PSU jumper on the second PSU
After you’ve shut down the PC, you can use the Killswitch on the back of the second PSU, and before turning on the PC engage the switch

[shumyeah]

Yes I should have mentioned it. I’ve tried a jumper as well.

Everytime I turned on the 2nd PSU first, and then the 1st one. Doesn’t work.

I just can’t get the 2nd PSU running but when I test it with a tester it works.