- A
The monitor's firmware is outdated
Why wrong: Firmware issues are rare and would likely cause other problems, not just refresh rate.
- B
The graphics card does not support 4K at 60Hz
Why wrong: If the GPU supports DP 1.2, it can do 4K 60Hz; the issue is more likely the cable.
- C
The DisplayPort cable is only rated for DisplayPort 1.1
DP 1.1 cables cannot handle the bandwidth for 4K 60Hz, forcing 30Hz.
- D
The monitor's refresh rate is set to 30Hz in the display settings
Why wrong: While this could be a setting, the user reports it only shows 30Hz, indicating a bandwidth limitation, not a config choice.
Question 703 of 1,020
DisplayPort 1.2 4K at 30Hz: Cable Bandwidth Problem
This 220-1201 practice question tests your understanding of display devices. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A user reports that their 4K monitor connected via DisplayPort 1.2 only shows a 30Hz refresh rate at native resolution, causing mouse movement to feel laggy. The monitor supports 60Hz at 4K. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Quick Answer
The answer is a DisplayPort cable only rated for DisplayPort 1.1. This is correct because while the DisplayPort 1.2 standard itself supports 4K at 60Hz, the physical cable must have sufficient bandwidth to carry that data; a DP 1.1 cable lacks the necessary throughput, capping the refresh rate at 30Hz despite the monitor and ports supporting 60Hz. On the CompTIA A+ Core 1 220-1201 exam, this question tests your understanding of cable bandwidth limitations versus port standards—a common trap is assuming the port alone dictates performance. Remember that a higher version port is useless without a matching cable. For a memory tip: think of it as a hose—a narrow DP 1.1 hose can’t deliver the full 4K 60Hz water flow, only a trickle at 30Hz.
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 DisplayPort cable is only rated for DisplayPort 1.1
DisplayPort 1.2 has sufficient bandwidth (17.28 Gbps) to support 4K at 60Hz with 8-bit color. However, a cable only rated for DisplayPort 1.1 is limited to 8.64 Gbps, which cannot handle the full data rate required for 4K at 60Hz, forcing the signal to drop to 30Hz. This is the most likely cause because the cable is a physical bottleneck, even though the GPU and monitor both support the higher refresh rate.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 monitor's firmware is outdated
Why it's wrong here
Firmware issues are rare and would likely cause other problems, not just refresh rate.
- ✗
The graphics card does not support 4K at 60Hz
Why it's wrong here
If the GPU supports DP 1.2, it can do 4K 60Hz; the issue is more likely the cable.
- ✓
The DisplayPort cable is only rated for DisplayPort 1.1
Why this is correct
DP 1.1 cables cannot handle the bandwidth for 4K 60Hz, forcing 30Hz.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The monitor's refresh rate is set to 30Hz in the display settings
Why it's wrong here
While this could be a setting, the user reports it only shows 30Hz, indicating a bandwidth limitation, not a config choice.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the misconception that the refresh rate issue is caused by a monitor setting or GPU limitation, when in fact the cable's bandwidth rating is the critical bottleneck that candidates overlook.
Trap categories for this question
Command / output trap
While this could be a setting, the user reports it only shows 30Hz, indicating a bandwidth limitation, not a config choice.
Detailed technical explanation
How to think about this question
DisplayPort 1.2 uses 4 lanes with a raw bit rate of 5.4 Gbps per lane, yielding 17.28 Gbps after 8b/10b encoding overhead. 4K at 60Hz with 8-bit RGB requires approximately 12.54 Gbps, which fits within DP 1.2 bandwidth. A DP 1.1 cable is only certified for 2.7 Gbps per lane (8.64 Gbps total), insufficient for 4K60, so the GPU and monitor negotiate a lower refresh rate (30Hz) to stay within the cable's limits. In practice, many users overlook cable specifications, assuming all DisplayPort cables are identical, leading to this exact symptom.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Display Devices — study guide chapter
Learn the concepts, then practise the questions
- →
Display Devices practice questions
Targeted practice on this topic area only
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Display Devices — This question tests Display Devices — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The DisplayPort cable is only rated for DisplayPort 1.1 — DisplayPort 1.2 has sufficient bandwidth (17.28 Gbps) to support 4K at 60Hz with 8-bit color. However, a cable only rated for DisplayPort 1.1 is limited to 8.64 Gbps, which cannot handle the full data rate required for 4K at 60Hz, forcing the signal to drop to 30Hz. This is the most likely cause because the cable is a physical bottleneck, even though the GPU and monitor both support the higher refresh rate.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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