Hi,
From what I have read I have seen many different ways to connect risers/gpus and atx+server psu
In my experience I have worked with ATX + Server PSU (HP 750W/1200W) and I can tell you what has been working for me:
- ATX PSU for Mobo+Couple GPUS and their risers.
- Server PSU for risers and GPUs.
- If you use more than one server psu, each GPU and their risers are in the same PSU
If you use breakout board will make the Server PSU on when ATX PSU is on. The system can work fine without it but Server PSU will be always on (GPUs + Risers). In some cases you would need to turn off Server PSU to recover the GPUs from a crash, rare but happens when finding the right overclock, nothing to worry if you have an stable system or if you can restart it physically.
Avoid:
Using different PSU for riser and gpu. Instead use the same PSU for the same GPU and its riser.
Using sata connectors for risers or using more than 2 risers per cable from ATX PSU.
You have to power the Server PSU first, because you need the motherboard to recognize the GPUs in the system. If you do it reversed, the system will not show the GPUs from Server PSU.
Cheers!