Why Does My PC Shut Down Under Load? Power Supply Troubleshooting for A+
A technician is building a new workstation with a high-end graphics card. The power supply is 650W 80+ Gold. The system boots and runs normally for basic tasks, but when the user launches a 3D rendering application, the computer shuts down immediately. The technician checks the GPU temperature and it stays below 70°C. Which of the following is the MOST likely cause?
Quick Answer
The answer is an insufficient power supply for the GPU under load. This is the most likely cause because a high-end graphics card can momentarily draw far more current than its rated TDP when transitioning from idle to a full 3D rendering workload, causing a 650W power supply to trip its overcurrent protection or drop below ATX voltage tolerances, which triggers an immediate shutdown. On the CompTIA A+ Core 1 220-1101 exam, this scenario tests your understanding of power supply sizing and the difference between sustained and peak power draw; a common trap is to blame overheating when the GPU temperature is actually normal. Remember that a system that runs fine on the desktop but crashes instantly under load is almost always a power delivery problem, not a thermal one. A useful memory tip is "Peak Pulls the Plug"—if the PSU can’t handle the peak current spike, the system shuts down to protect itself.
⚠ Common exam trap
CompTIA often tests the distinction between symptoms of power insufficiency versus driver or thermal issues, and the trap here is that candidates may assume a 650W PSU is always sufficient for any single GPU, ignoring the specific power draw of high-end cards under load and the importance of transient spikes.
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 insufficient for the GPU under load.
The 650W 80+ Gold power supply is likely insufficient to handle the peak power draw of a high-end graphics card under full 3D rendering load. When the GPU transitions from idle to maximum load, it can draw significantly more current, causing the PSU to trip its overcurrent protection or drop voltage below the ATX specification, resulting in an immediate shutdown. The fact that the system works for basic tasks but fails under load points directly to a power delivery issue, not a thermal or driver problem.
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 power supply is insufficient for the GPU under load.
Why this is correct
The GPU's transient power spikes under 3D rendering push the 650W 80+ Gold unit past its sustained output, tripping its overcurrent protection and cutting power instantly. Temperatures stay normal because the shutdown is electrical, not thermal. A higher-wattage PSU with adequate 12V rail headroom satisfies the load constraint.
- ✗
The GPU drivers are outdated.
Why it's wrong here
Outdated drivers cause rendering artefacts, crashes within the application, or black screens, not an instantaneous full-system power-off under load. Driver updates are the right fix when a GPU misbehaves only inside specific applications while the machine otherwise stays powered. Here the shutdown pattern points to the PSU's 12V rail collapsing under the GPU's transient spike.
- ✗
The motherboard BIOS needs an update for the GPU.
Why it's wrong here
A BIOS lacking GPU support prevents the card initialising at all, so the system would fail POST or show no display, not run basic tasks fine. BIOS updates address compatibility with newly released cards before first boot, which is not this symptom.
When this WOULD be correct
A technician installs a new GPU, and the system fails to boot or shows no display. The motherboard BIOS is older and lacks support for the GPU's UEFI GOP or PCIe version, requiring a BIOS update to enable proper initialization.
- ✗
The CPU is overheating.
Why it's wrong here
A CPU thermal shutdown would also occur under sustained all-core loads, not only when the GPU is stressed; the GPU temperature reading already rules out graphics overheating. CPU cooling is the correct suspect when crashes track processor-intensive workloads such as video encoding.
When this WOULD be correct
A question where a computer shuts down during CPU-intensive tasks (e.g., video encoding) and CPU temperature exceeds safe limits (e.g., >90°C) would make CPU overheating the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓The power supply is insufficient for the GPU under load.Correct answer▾
Why this is correct
The GPU's transient power spikes under 3D rendering push the 650W 80+ Gold unit past its sustained output, tripping its overcurrent protection and cutting power instantly. Temperatures stay normal because the shutdown is electrical, not thermal. A higher-wattage PSU with adequate 12V rail headroom satisfies the load constraint.
✗The motherboard BIOS needs an update for the GPU.Wrong answer — click to see why▾
Why this is wrong here
The system boots and runs normally for basic tasks, and the issue only occurs under GPU load. An outdated BIOS typically causes boot failures, instability at idle, or failure to recognize the GPU, not a shutdown only during high load.
★ When this WOULD be the correct answer
A technician installs a new GPU, and the system fails to boot or shows no display. The motherboard BIOS is older and lacks support for the GPU's UEFI GOP or PCIe version, requiring a BIOS update to enable proper initialization.
Why candidates choose this
Candidates may confuse GPU compatibility issues with power-related shutdowns, assuming that a BIOS update is needed for newer hardware, but the symptom of shutdown under load points to power delivery rather than compatibility.
✗The CPU is overheating.Wrong answer — click to see why▾
Why this is wrong here
The system shuts down immediately under GPU load, but the CPU overheating would typically cause throttling or shutdown after sustained load, not instantly. The GPU temperature is normal, and the CPU is not mentioned as hot.
★ When this WOULD be the correct answer
A question where a computer shuts down during CPU-intensive tasks (e.g., video encoding) and CPU temperature exceeds safe limits (e.g., >90°C) would make CPU overheating the correct answer.
Why candidates choose this
Candidates may associate sudden shutdowns with overheating, and since the GPU is cool, they might incorrectly assume the CPU is the culprit without considering power supply limitations.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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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 building a desktop computer for a user. The power supply unit (PSU) is a 750W unit with a single 12V rail. The graphics card requires two 8-pin PCIe power connectors. The PSU has two separate cables, each with one 6+2 connector. The technician instead uses a single cable that has two 6+2 connectors daisy-chained (one at the end, one in the middle) to power the graphics card. The system boots and runs normally under light load, but under heavy gaming load, the system shuts down. Which of the following is the MOST likely cause of this issue?
medium- A.The PSU does not have enough wattage for the graphics card.
- ✓ B.The daisy-chained cable cannot deliver sufficient current to both connectors, causing voltage drop and shutdown.
- C.The graphics card requires a power supply with dual 12V rails.
- D.The PCIe slot is not providing enough power.
Why B: The daisy-chained cable is designed to deliver a maximum current per connector, typically around 150W per 8-pin PCIe connector. When both connectors are on the same cable, the total current draw can exceed the cable's rated capacity (often 288W for 18AWG wire), causing voltage drop and triggering the PSU's overcurrent protection (OCP) or causing instability under heavy load. This results in the system shutting down during gaming, even though the PSU's total wattage (750W) is sufficient.
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.