From Earlham Cluster Department
In order to determine the characteristics of a power supply capable of power one of our subracks, we needed to generate detailed information on the power consumption of a single node. The total AC amperage and the DC amperage per wire on each of the standard ATX connectors comprise a single node power consumption profile. Additionally, a separate power consumption profile for different load conditions are used to determine the maximum power output capacities the power supply would need.
The total AC amperage is measured by an power meter inline between the wall jack and the power supply. Every wire in each connector that powers the motherboard was cut and reconnected to a terminal block. A multi-meter was then inserted to measure the DC amperage used by each voltage rail.
The largest of the total DC amperages used by each rail determine the maximum output capacities needed on each rail of the power supply for a single node.
Multiplying the single node values by a factor of four results in the necessary characteristics of a power supply needed to power a subrack of four nodes.
<4 node summary table>