Examkin

Question

Difficulty: HardCPU Architecture Cooling and Sockets

A systems administrator replaces a degraded cooling assembly on a heavily utilized server processor. After powering on the system, the server immediately experiences severe thermal throttling under load despite the new heatsink fan operating at maximum rated RPM and thermal compound having been applied correctly. Touch inspection reveals that the baseplate resting against the CPU integrated heat spreader (IHS) is extremely hot, whereas the copper heat pipes and aluminum cooling fins near the exhaust fan remain completely cold. Which of the following component failures best explains this thermal symptom?

  1. Loss of vacuum envelope or working fluid leakage within the heat pipes, preventing liquid-to-vapor phase-change heat transferAnswer
  2. B
    Incorrect POST beep code interpretation causing the system to misreport fan speed control signals as CPU over-temperature alerts
  3. C
    Excessive virtual machine memory and vCPU overcommitment on the hypervisor causing physical hardware thermal sensor saturation
  4. D
    Undercalculating system power supply unit wattage, leading to insufficient power delivery to the CPU heat pipe thermal pump

Answer

Loss of vacuum envelope or working fluid leakage within the heat pipes, preventing liquid-to-vapor phase-change heat transfer
Heat pipes are sealed copper tubes containing a fluid under low pressure (vacuum) and a porous wick structure. Thermal energy from the CPU vaporizes the fluid at the hot baseplate. The vapor travels to the cooler fin stack, condenses back into liquid as heat is dissipated by the fan, and travels back to the base via capillary action. If a heat pipe loses its vacuum seal or leaks its fluid, phase-change thermal transfer ceases, causing heat to pool at the baseplate while the radiator fins remain cold.

Step-by-Step Solution

1
Analyze the physical thermal differential reported in the scenario
The CPU baseplate touching the IHS is hot, but the heat pipes and cooling fins remain cold.
This indicates heat is not being conducted away from the CPU base to the radiator fins.
2
Evaluate the thermal transfer mechanics of heat pipe cooling systems
Heat pipes require a sealed internal chamber under vacuum containing a small amount of working fluid (such as distilled water or alcohol).
Heat evaporates the fluid at the hot CPU end; the vapor travels to the cooler fin end, condenses back to liquid, and returns to the base via a capillary wick structure.
3
Identify the cause of total thermal conduction failure across the heat pipe assembly
A rupture, micro-crack, or manufacturing defect that breaches the sealed vacuum causes the working fluid to escape or fail to evaporate/condense.
Without phase-change mechanics, hollow metal pipes conduct very little heat, causing extreme CPU temperatures at the baseplate while fins stay cold.

Key Concept

Heat Pipe Phase-Change Cooling Dynamics and Failure Modes
Rate this question

Topics

CPU Architecture Cooling and Sockets

More questions from this topic