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220-1201 Practice Question: During a system boot, a user sees an error…
During a system boot, a user sees an error message: 'CMOS checksum error - Defaults loaded.' The system then boots normally but loses the date and time settings after power-off. What is the most likely hardware failure?
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 motherboard's CMOS battery is depleted or failing.
The CMOS checksum error indicates that the BIOS settings are corrupted or not being retained. The date/time resetting after power-off points to a failing or dead CMOS battery, which powers the volatile memory that stores these settings when the system is off.
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 UEFI firmware has become corrupted and needs reflashing.
Why it's wrong here
UEFI firmware corruption typically manifests as a complete failure to boot, system instability, or critical errors during the Power-On Self-Test (POST), as the core instructions for hardware initialization are compromised. A checksum error specifically related to CMOS settings and a loss of date/time points to the volatile memory retaining these settings, not the non-volatile firmware itself. Reflashing is a drastic measure for severe firmware issues, not typically for a simple settings reset.
- ✓
The motherboard's CMOS battery is depleted or failing.
Why this is correct
The Complementary Metal-Oxide-Semiconductor (CMOS) battery provides continuous power to the CMOS RAM chip, which stores the system's BIOS/UEFI settings and the Real-Time Clock (RTC) when the computer is powered off or unplugged. When this battery depletes, the CMOS RAM loses power, causing the stored configuration (including date, time, and boot order) to revert to default values. This often triggers a "CMOS Checksum Error" during boot as the system detects the settings have been lost or corrupted.
- ✗
The power supply unit is not providing enough standby power.
Why it's wrong here
The Power Supply Unit (PSU) provides a +5VSB (5 Volt Standby) rail, which powers components like USB ports for charging, Wake-on-LAN functionality, and the power button circuit when the system is off. However, this standby power does not directly maintain the volatile CMOS RAM that stores BIOS/UEFI settings and the real-time clock. The CMOS battery is a dedicated, independent power source specifically for preserving these settings, even when the PSU is completely disconnected from AC power.
- ✗
The hard drive is failing and corrupting the boot sector.
Why it's wrong here
A failing hard drive or a corrupted boot sector primarily affects the operating system's ability to load, leading to errors such as "Operating System not found," "Non-system disk or disk error," or infinite boot loops. These issues are distinct from CMOS checksum errors and date/time resets, which are indicative of problems with the motherboard's firmware settings retention. The hard drive's integrity does not influence the power supply to the CMOS RAM chip.
Go deeper
Related to this question
Learn chapter
Laptop Hardware and Components
Key term
BIOS
BIOS (Basic Input/Output System) is the low-level firmware stored on a motherboard chip that initializes and tests hardware components before loading the operating system.
Key term
CMOS
CMOS is a small memory chip on a computer motherboard that stores important system settings like date, time, and hardware configuration, even when the power is off.
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Same concept, more angles
1 more way this is tested on 220-1201
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 user complains that their computer boots slowly and shows a 'Press F1 to continue' message every time. The firmware settings appear to have lost their configuration. What is the most likely cause?
medium- A.The boot order is incorrect
- ✓ B.The CMOS battery is failing
- C.The hard drive is failing
- D.The BIOS version is outdated
Why B: A failing or depleted CMOS battery cannot retain BIOS settings, causing defaults to load and often requiring user intervention at boot. This is a common issue that leads to the 'Press F1' prompt. The question tests understanding of CMOS battery function in maintaining firmware settings.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1201 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 220-1201 exam.