I am thoroughly confused...

[nerdboy20]

I have received some Dell Precision Tower 3620 units. They are running i7-6700 8 GB DDR4 and came with 365W Power Supplies and Quadro M4000 video cards. 

 

I am upgrading them to be able to play modern games so I am adding a different video card and power supply. They have fresh installs of Win 10 Pro and the latest drivers. 

 

They work great with the 365W PSU and Quadro cards for benchmarking in 3DMARK Time Spy and Firestorm on the basic edition.

They work great with GTX 750 Ti / 1050 Ti and 1650 with the stock power supply in 3DMARK.

 

It is when I change out the power supply that things get worse. Started with Time Spy loading and then reboots and then does the same with Firestrike. 

I have tried these video cards:

GTX 1060 6GB (6 pin for power), R9 Nano 4GB and RX 580 8 GB (both are 8 pin for power)

I have tried these power supplies:

Seasonic S12II-520GB / Corsair CX600 / Corsair HX750i

 

What worked is:
The HX750i with the Nano card worked perfectly in the Precision running Time Spy and Firestrike. It just is too big and can not fit in the case.

 

Confusion is:
When I took the Nano and the Seasonic power supply and plugged it into a Optiplex 9020 it worked perfectly fine running the benchmarks. Even though it failed on the Precision.

 

Has anyone had this problem before?