A technician is assembling a dual-processor workstation. Upon pressing the power button, system fans spin for approximately one second before the machine abruptly powers down completely. The motherboard standby light remains illuminated, but the power button becomes unresponsive until AC power is toggled off and back on. Removing all storage drives, peripherals, and expansion cards does not resolve the issue. However, when the 8-pin EPS12V power cable dedicated to CPU 2 is disconnected from the motherboard, system fans power on continuously and POST diagnostic beep codes sound for unpopulated memory slots. Which of the following is the most likely root cause of the initial shutdown?
- A short circuit or failed voltage regulator module (VRM) on the power plane for CPU 2 triggering power supply protection mechanismsAnswer
- BInadequate total wattage from the power supply failing to meet the initial peak inrush current required for dual processors
- CCorrupted UEFI/BIOS firmware preventing the system from initializing the POST hardware diagnostic sequence
- DIncorrect RAM channel slot population causing the integrated memory controller on CPU 2 to halt system execution
Answer
A short circuit or failed voltage regulator module (VRM) on the power plane for CPU 2 triggering power supply protection mechanisms
When a power supply detects an active low-impedance short circuit—such as a shorted MOSFET in the voltage regulator module (VRM) powering CPU 2—its short-circuit protection (SCP) immediately cuts main power to prevent component fire or physical trace destruction. Disconnecting the 8-pin EPS12V auxiliary power cable removes the shorted circuit path from the motherboard's +12V power distribution network, enabling the power supply to maintain steady power to the rest of the board.
Step-by-Step Solution
Key Concept
Identifying Power Supply Unit (PSU) short-circuit protection triggers caused by motherboard VRM component failures