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Difficulty: MediumMotherboard, RAM, CPU, and Power Issues

A technician is assembling a desktop workstation. Upon pressing the power button, the chassis fans spin and internal status LEDs illuminate continuously, but the system fails to perform a Power-On Self-Test (POST), displays no video output, and produces no audible beep codes. The technician confirms that the 24-pin ATX power connector is securely attached to the motherboard. Which of the following is the most likely cause of this issue?

  1. The 8-pin EPS12V CPU power connector is disconnected.Answer
  2. B
    The bootloader on the main system storage drive is corrupted.
  3. C
    The installed memory modules are configured in single-channel mode.
  4. D
    An SO-DIMM memory module was installed instead of a standard DIMM.

Answer

The 8-pin EPS12V CPU power connector is disconnected.
The correct answer identifies that the 8-pin EPS12V auxiliary power cable is disconnected. Modern desktop processors draw dedicated power through this connector near the CPU socket. Without this connection, the CPU receives no power, keeping the system from executing POST routines or displaying video, while chassis fans and motherboard LEDs continue to operate via power from the primary 24-pin ATX connector.

Step-by-Step Solution

1
Analyze system power symptoms and POST status
Fans spin and LEDs light up via 24-pin ATX power, but no POST occurs and no display output or beep codes are present.
This indicates that basic standby power and fan circuits are active, but the central processor is not powering on to execute BIOS/UEFI POST instructions.
2
Verify CPU power delivery connections
Modern desktop motherboards require a separate 4-pin or 8-pin EPS12V power cable connected directly near the CPU socket.
If the auxiliary CPU power connector is omitted, the CPU remains unpowered, halting hardware initialization before video initialization or diagnostic beep codes can be issued.

Key Concept

CPU Power Supply Requirements and Initial Hardware Diagnostic Indicators
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Topics

Motherboard, RAM, CPU, and Power Issues

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