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Difficulty: MediumRAM Types and Characteristics

A technician is upgrading a desktop workstation used for video editing. The motherboard specifications state that it requires DDR4 Unbuffered DIMMs (UDIMMs). The technician attempts to install two 16 GB DDR4 Registered DIMM (RDIMM) modules retrieved from a retired enterprise server. Upon powering on the workstation, system fans turn on, but the computer fails to POST and displays no video output. Which of the following best explains why the system failed to boot?

  1. Registered memory (RDIMMs) contains an onboard register buffer that is incompatible with desktop motherboards designed solely for unbuffered memory.Answer
  2. B
    Registered memory modules utilize the compact SO-DIMM physical form factor, which prevents proper seating into full-sized desktop motherboard slots.
  3. C
    Installing two memory modules into adjacent slots automatically forces the motherboard memory controller to halt POST due to a dual-channel configuration error.
  4. D
    Registered RAM modules require an M.2 host bus controller slot rather than traditional DDR4 motherboard expansion slots.

Answer

Registered memory (RDIMMs) contains an onboard register buffer that is incompatible with desktop motherboards designed solely for unbuffered memory.
Registered memory (RDIMM) incorporates an onboard register chip that buffers control and address signals to increase stability in high-density server environments. Standard desktop motherboards and consumer CPUs lack support for this register interface and require Unbuffered memory (UDIMM), causing the computer to fail POST when RDIMMs are installed.

Step-by-Step Solution

1
Analyze motherboard memory specifications
The desktop motherboard explicitly specifies support for DDR4 Unbuffered DIMMs (UDIMMs).
Desktop motherboards rely on the CPU's integrated memory controller directly addressing memory chips without an intermediate buffer register.
2
Compare installed module characteristics (RDIMM vs UDIMM)
RDIMMs contain an extra register chip that buffers command and address signals between the memory controller and the DRAM chips.
This buffer reduces electrical loading in multi-slot server boards, but desktop chipsets cannot communicate through this register architecture.
3
Determine the root cause of the POST failure
The system cannot initialize RAM during POST due to hardware protocol incompatibility between the desktop chipset and the registered memory modules.
Incompatible memory architecture prevents successful system boot and Power-On Self-Test (POST).

Key Concept

UDIMM vs RDIMM Compatibility
Estimated Time:1m 0s
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Topics

RAM Types and Characteristics

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