Asus ESC4000/IB - Manual (Page 68)

4-14 Chapter 4: Motherboard information
8. SSI power connectors (20-pin PWR1, 8-pin PWR2)
These connectors are for an SSI power supply plugs. The power supply plugs
are designed to fit these connectors in only one orientation. Find the proper
orientation and push down firmly until the connectors completely fit.
• DO NOT forget to connect the 20+8-pin power plugs; otherwise, the system
will not boot up.
• Use of a PSU with a higher power output is recommended when configuring
a system with more power-consuming devices. The system may become
unstable or may not boot up if the power is inadequate.
• Ensure that your power supply unit (PSU) can provide at least the minimum
power required by your system.