What is the difference between VXIbus Mainframe total+ usable power?

What is the difference between VXIbus Mainframe total+ usable power?

Total power is the maximum power that the power supply can provide. Total power is the sum of V * I for each power rail. VXI power supplies provide 7 voltage rails (24, 12, 5, -2, -5.2, -12, -24). If a power supply only supplied one voltage rail, then total power and usable power would be the same. Since VXI power supplies have 7 rails, they typically cannot drive all 7 rails at maximum current at the same time. Usable power is the most wattage that the power supply can provide at one time. Since usable power is really the maximum output power, total power is relatively meaningless. Usable power specifications are the primary concern of most VXIbus test system integrators.