Question What ATX Type Power Supply can be Used without a Motherboard to Power Multiple 12V/5V HDDs?

May 24, 2021
What ATX Type Power Supply can be Used without a Motherboard to Power Multiple 12V/5V HDDs?

I've used a repurposed server power supply for years, it has gone out, my drives are newer and since changed from molex LP4 connections to all SATA Power connections. The only other power that I would possibly need is a 4-Pin PWM controlled power source, but I have not found a new controller that doesn't use the output on a motherboard. Currently there are 6 drives in my rack that I am powering and there is no motherboard present. Size is not an issue and I really don't require all the features of an ATX PSU like 3.3V, 5VSB or -12V. I had considered a Fully Modular Power Supply however, I have been trying an ATX power supply that uses a "Test Connector" which shorts the wire to turn on the power supply. I've been having a problem with the 5V maintaining 5V after the power supply is warmed up, someone told me that is typically from the motherboard not being attached to the power supply. I don't require a motherboard for my application so one would never be attached to the connector.


Apr 19, 2021
Just pick an old, simple ATX power supply, once you short the pin it will stay ON as long as you want, I used to have a standalone ATX power supply that runs 24/7 to power some LED lights.

Some newer PSU may have a voltage sensor so it could detect the absence of a motherboard, but the old PSU don't care about that.


Not very many independent PWM fan hubs out there, no.

5V failing to stay in spec speaks to an old regulated power supply design. When the load on the 5V and 12V isn't balanced (they design it around a typical whole computer) then it gets out of specification.

What you want is an ATX power supply that uses DC-DC converters internally for 5V and 3.3V. Typically these are going to be the more efficient ones, check for reviews on power supplies in your price range. Might check out some STX power supplies as well, they are smaller and pretty much always use DC-DC converters.

What you don't want is an old power supply, that is exactly the problem you are facing.