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Question

Difficulty: MediumVideo, Display, and Projector Issues

An employee connects a newly issued 4K4\text{K} resolution monitor to their workstation's dedicated graphics card using an older, unrated video cable found in storage. Although the display powers on and displays an image, the maximum selectable refresh rate in the operating system settings is capped at 30 Hz30\text{ Hz}, and screen flickering occurs when attempting higher resolutions. The technician confirms that the graphics card driver is up to date and fully supports 4K4\text{K} output at 60 Hz60\text{ Hz} and above. Which of the following is the most likely cause of this issue?

  1. The video cable lacks the bandwidth capacity required for the higher resolution and refresh rate combination.Answer
  2. B
    The video card's VRAM is thermal throttling and causing artifacting during signal handshakes.
  3. C
    The monitor's high-voltage backlight inverter is failing to supply stable power to the display matrix.
  4. D
    The motherboard system BIOS must be updated before installing high-resolution external monitors.

Answer

The video cable lacks the bandwidth capacity required for the higher resolution and refresh rate combination.
Display resolution and refresh rate output depend directly on cable bandwidth. When an older or lower-standard cable (such as standard HDMI 1.4 or single-link cable) is used for a 4K4\text{K} screen, the available throughput is insufficient for 4K4\text{K} at 60 Hz60\text{ Hz} or higher. Consequently, Extended Display Identification Data (EDID) negotiation limits the selectable refresh rate in the operating system to 30 Hz30\text{ Hz}, and forcing higher bandwidth leads to signal loss or flickering.

Step-by-Step Solution

1
Analyze the reported symptoms and environment.
The display functions at 4K4\text{K} resolution but restricts refresh rates to 30 Hz30\text{ Hz} and flickers when pushed further, despite verified GPU driver capability.
Display resolution and refresh rate limits are determined by the combined capabilities of the GPU, monitor panel, and interconnect cable.
2
Evaluate the interconnecting cable specs.
Using an unrated or older specification cable limits total data throughput bandwidth.
Higher resolutions (4K4\text{K}) paired with higher refresh rates (60 Hz+60\text{ Hz}+) require high bandwidth cables (e.g., HDMI 2.0+ or DisplayPort 1.2+). Legacy or cheap cables trigger Display Data Channel (DDC) bandwidth restrictions.
3
Select the correct diagnostic conclusion.
Replacing the legacy cable with a certified High Speed / Ultra High Speed cable will resolve the bandwidth constraint.
Cable throughput mismatch is the root cause of capped refresh rates and signal flickering in high-resolution setups.

Key Concept

Display Cable Bandwidth and Refresh Rate Limitations
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Topics

Video, Display, and Projector Issues

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