Why Your PC Freezes Under Load: Diagnosing a Failing Power Supply
A technician is troubleshooting a desktop computer that experiences intermittent freezing, especially when running graphics-intensive applications or games. The technician has updated all drivers, run full antivirus scans, and replaced the RAM. The CPU and GPU temperatures stay below 70°C under load. The event logs show no critical errors. However, the freezing always occurs under high load, and sometimes the system restarts without a blue screen. Which component is MOST likely failing?
Quick Answer
The answer is the power supply unit (PSU). This is correct because intermittent freezing under load with no blue screen, especially during graphics-intensive tasks, points directly to unstable power delivery; when the CPU and GPU demand peak current, a failing PSU can’t maintain the required +12V rail voltage, causing the system to lock up or restart without logging critical errors. On the CompTIA A+ Core 1 220-1101 exam, this scenario tests your ability to differentiate power issues from thermal or memory failures—a common trap is chasing software or driver fixes when the hardware power source is the root cause. Remember that normal temperatures and replaced RAM eliminate overheating and memory faults, leaving the PSU as the prime suspect. A handy memory tip: “If it freezes under load but stays cool, check the power rule.”
⚠ Common exam trap
CompTIA often tests the trap that candidates assume high temperatures are the only cause of load-related freezes, leading them to choose the CPU or GPU, but the PSU’s inability to deliver stable power under peak demand is a more subtle and common cause of intermittent restarts without error logs.
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
✓
Power supply unit (PSU)
The power supply unit (PSU) is the most likely failing component because intermittent freezing and restarts under high load, without blue screens or critical errors, are classic symptoms of an unstable or insufficient power supply. When the GPU and CPU draw maximum current during graphics-intensive tasks, a failing PSU may drop below required voltage rails (e.g., +12V), causing the system to lock up or reboot. The fact that temperatures are normal and RAM has been replaced eliminates thermal and memory issues, pointing directly to power delivery.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Power supply unit (PSU)
Why this is correct
Intermittent freezes and restarts under high load, with temperatures, RAM, drivers, and logs cleared, point to the PSU failing to sustain increased power draw. Graphics-intensive workloads raise GPU and CPU demand, exposing the degraded rail.
- ✗
CPU
Why it's wrong here
A failing CPU generally triggers WHEA machine-check exceptions, thermal throttling, or blue screens, none of which appear here. The load-correlated restarts with no logged errors fit a PSU whose 12V rail collapses under transient draw. CPU replacement is indicated by calculation errors or thermal shutdowns.
- ✗
GPU
Why it's wrong here
GPU faults usually produce artefacts, driver timeouts (TDR events), or display loss, and temperatures here remain below 70°C. Freezing and restarts without a blue screen under high load indicate the PSU cannot sustain transient power demand. A GPU would be the answer if artefacts or display corruption appeared.
- ✗
Motherboard
Why it's wrong here
Motherboard faults typically cause POST failures, USB or slot dropouts, or capacitor-related instability rather than load-correlated restarts. The pattern of failure scaling with power draw and no logged errors points to the PSU's inability to sustain 12V rails under transient GPU load. Motherboard replacement would be indicated by boot or device-detection faults.
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Key term
Power supply unit
A power supply unit (PSU) is the hardware component that converts electricity from a wall outlet into usable power for a computer's internal components.
Key term
Dual In-line Memory Module
A Dual In-line Memory Module (DIMM) is a small circuit board that holds memory chips and plugs into a computer's motherboard to provide Random Access Memory (RAM).
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Same concept, more angles
2 more ways 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 randomly powers off. The event log shows a critical error: Kernel-Power 41. The power supply unit (PSU) fan is spinning, and the CPU cooler fan is also spinning. All cables appear connected. Which of the following should the technician do NEXT?
medium- A.Replace the CPU
- ✓ B.Check for a faulty power supply using a multimeter
- C.Reinstall the operating system
- D.Update the BIOS firmware
Why B: The Kernel-Power 41 error indicates an unexpected shutdown, often caused by a failing power supply. Even though the PSU fan spins, it may not deliver stable voltages under load. Using a multimeter to check the PSU's output voltages (e.g., +3.3V, +5V, +12V) is the correct next step to isolate the issue before replacing components.
Variation 2. A technician is troubleshooting a desktop computer that randomly freezes and then reboots. The technician runs a CPU stress test; after about 5 minutes, the system freezes and reboots. The CPU temperature during the test is monitored and never exceeds 75°C. The technician has run a full memory test (MemTest86) and a hard drive diagnostic (SMART check); both pass without errors. The power supply voltages are within specifications when measured with a multimeter at idle and under load. Which of the following is the MOST likely cause of the issue?
hard- A.Insufficient voltage to the CPU due to motherboard VRM failure
- ✓ B.A failing power supply unit
- C.A corrupted operating system driver
- D.A failing system fan that spins intermittently
Why B: The symptoms—random freezing and rebooting under CPU stress, with all other components (CPU temperature, memory, storage, and power supply voltages) passing diagnostics—point to a failing power supply unit (PSU). Even though the multimeter shows correct voltages at idle and under load, a PSU can fail intermittently under sustained high current draw, causing voltage ripple or transient drops that trigger a system reset. The CPU stress test specifically taxes the 12V rail, and a marginal PSU may not maintain stable output during extended high-load scenarios, leading to the observed behavior.
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.