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Difficulty: HardMotherboard, RAM, CPU, and Power Issues

A field technician is inspecting a desktop workstation that fails to complete POST following a memory upgrade. When powered on, the power LED turns solid, system fans spin continuously at maximum speed, and the motherboard emits a repeating pattern of three short beeps with no display output. The user mentions forcing a 260-pin SO-DIMM module into the expansion slot because it was listed as high-performance DDR4 RAM online. Which of the following best identifies the root cause of this system failure?

  1. The 260-pin SO-DIMM module is physically and electrically incompatible with standard desktop motherboard slots, which require 288-pin DIMM modules.Answer
  2. B
    The POST beep sequence indicates corrupted BIOS/UEFI firmware that must be re-flashed before system RAM can be initialized.
  3. C
    The laptop display inverter has suffered an electrical short, causing the system motherboard to halt boot operations during power-on initialization.
  4. D
    The installed memory module was configured in single-channel orientation rather than alternating dual-channel motherboard slots.

Answer

The 260-pin SO-DIMM module is physically and electrically incompatible with standard desktop motherboard slots, which require 288-pin DIMM modules.
The correct answer highlights the form-factor mismatch between standard desktop motherboard DIMM slots (288 pins) and mobile SO-DIMM memory modules (260 pins). Because the pins and physical alignment key do not match, the motherboard memory controller cannot detect valid RAM, prompting the BIOS/UEFI to halt POST and emit a series of memory-error beep codes.

Step-by-Step Solution

1
Analyze the reported hardware symptoms and physical setup.
The desktop workstation powers on with spinning fans and solid power lights, but halts at POST with a repeating 3-beep memory warning code.
Three POST beeps standardly indicate a memory initialization or detection failure on most BIOS/UEFI systems.
2
Evaluate the user's memory upgrade choice.
The user attempted to insert a 260-pin SO-DIMM module into a desktop motherboard slot.
SO-DIMM (Small Outline Dual In-line Memory Module) is a smaller form factor engineered specifically for laptops and compact systems, whereas standard desktop motherboards require full-length 288-pin DIMM modules.
3
Identify the primary root cause.
Physical and electrical pin mismatch prevents the motherboard memory controller from contacting or initializing the RAM stick.
The notch positioning and total pin count differ between DIMM and SO-DIMM form factors, causing a fatal POST memory detection halt.

Key Concept

RAM Form Factors and POST Error Diagnostics
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Topics

Motherboard, RAM, CPU, and Power Issues

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