[SOLVED] PC won't post when using 2 PSU

[dan_729]

Mining Build:

PSU #1 - RM1000i
B450 Tomahawk MAX
Ryzen 5 3400G (4+4)
Kingston 240GB SSD
2 x PCI-e Riser (Molex)
2 x Asus Strix RTX 3070 (8+8)

PSU #2 - RM1000i
2 x PCI-e Riser (Molex)
2 x Asus Strix RTX 3070 (8+8)


Condition #1
Both PSUs connected together to the Mobo via a Dual PSU 24-Pin Adapter Cable
Outcome:
PC won't post, everything else nominal (i.e. Both PSU turns on, CPU fan spins, Mobo led turns on, etc).
PC won't post again afterwards using only PSU #1, unless CMOS is reset or CPU is reconnected to socket.


Condition #2 & #3
Only PSU #1 active
Only PSU #1 active; but connected to the Mobo via a Dual PSU 24-Pin Adapter Cable instead
Outcome:
PC posts, everything nominal.


Condition #4
PSU #2 are NOT connected together to the Mobo via a Dual PSU 24-Pin Adapter Cable
Outcome:
PSU #2 GPUs power socket starts blinking red
Post status UNCLEAR since I manually forced shutdown right away

 

[dan_729]

Solved it, turns out I had to connect all PCI-e Risers (Molex) into the main PSU (the one that is connected to the Mobo via 24-pin), while also having the second PSU linked to the main one with the Dual PSU 24-Pin Adapter Cable.