Computer Shuts Down Under Load: Insufficient Power Supply
A user reports that their desktop computer shuts down unexpectedly when running resource-intensive applications like video editing. The technician has cleaned the dust from the heatsink and fans, verified that all fans are spinning, and monitored temperatures. The BIOS reports CPU temperature as 35°C idle and 70°C under load, which are within normal specifications. The system has a dedicated graphics card that requires a 6-pin PCIe power connector, and the power supply is a 450W unit that came with the computer case. Which of the following is the MOST likely cause?
Quick Answer
The answer is an inadequate power supply, as the system’s 450W unit is insufficient for the peak power draw under load. When a computer shuts down under load with a low wattage power supply, the PSU’s overcurrent protection or voltage sag triggers a sudden shutdown to prevent damage, even though temperatures and cooling are normal. On the CompTIA A+ Core 1 220-1101 exam, this scenario tests your ability to distinguish power-related failures from thermal or driver issues—a common trap is assuming overheating is the culprit when fans are clean and CPU temps are fine. Remember that a dedicated GPU with a 6-pin PCIe connector can draw 150W or more alone, and a generic case-included 450W PSU often delivers far less on the 12V rail than its label suggests. For the exam, keep this memory tip handy: “If temps are fine but the system dies, suspect the PSU’s size.”
⚠ Common exam trap
The trap here is that candidates focus on thermal issues (cleaning, fans, paste) and ignore the power supply, assuming that if temperatures are normal, the shutdown must be caused by a component failure like a bad capacitor or RAM, rather than an inadequate PSU that cannot sustain peak load.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The power supply is inadequate for the system's peak power draw
The system shuts down under load despite normal CPU temperatures and clean cooling. A 450W power supply that came with a case is typically a low-quality unit with limited capacity. The dedicated graphics card, especially during video editing, can draw significant power, and the total system peak draw likely exceeds the PSU's capacity, causing it to trip overcurrent protection or shut down.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The CPU thermal paste has degraded and needs to be reapplied
Why it's wrong here
Degraded thermal paste would push load temperatures well above 70°C, yet the BIOS already reports normal figures, so the CPU is not overheating. Reapplying paste is the right fix when idle or load temperatures climb abnormally despite clean fans and correct mounting.
- ✓
The power supply is inadequate for the system's peak power draw
Why this is correct
A 450W power supply may not provide enough power for a dedicated GPU and CPU under full load, causing the system to shut down to protect components. This is the most likely cause given the symptoms and normal temperatures.
- ✗
The motherboard has a faulty capacitor
Why it's wrong here
A faulty capacitor usually causes random instability, boot problems or visible bulging, not reproducible shutdowns tied specifically to high load. It is tempting because capacitors regulate power, but the consistent load-correlated pattern with a 450W supply and 6-pin PCIe GPU indicates insufficient PSU capacity.
- ✗
The RAM is incompatible with the motherboard
Why it's wrong here
Incompatible RAM typically causes boot failures, POST errors or instability, not load-dependent shutdowns. It is tempting because memory faults can crash systems, but the pattern here — shutdowns only under heavy load with a 450W supply and a 6-pin PCIe GPU — points to power delivery, not memory compatibility.
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Same concept, more angles
1 more way this is tested on 220-1101
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is troubleshooting a desktop computer that shuts down unexpectedly after about 15 minutes of running a graphics-intensive application. The computer operates normally during light use, such as web browsing and word processing. The technician has verified that all cooling fans are spinning and that the CPU and GPU temperatures are within normal ranges. Which of the following is the MOST likely cause of the issue?
medium- A.Failing memory module
- B.Corrupt operating system files
- ✓ C.Insufficient power supply capacity
- D.Faulty motherboard
Why C: The symptom of a computer shutting down under heavy GPU/CPU load after a consistent time interval, despite normal temperatures and fan operation, strongly points to the power supply unit (PSU) being unable to deliver sustained peak current. Graphics-intensive applications draw high transient power spikes; if the PSU's rated capacity is insufficient or its 12V rail is degraded, the overcurrent protection (OCP) or undervoltage protection (UVP) will trip, causing an abrupt shutdown. The fact that light workloads run fine confirms the issue is load-dependent, not a thermal or component failure.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.