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Difficulty: HardDisplay Cables and Connectors

An IT technician is deploying a portable workstation for a graphic designer who requires an external 4K monitor operating at 60 Hz, alongside high-speed data transfer for an external RAID storage array connected to the monitor's integrated hub. The technician connects the laptop's Thunderbolt 4 port to the monitor's USB-C video input using a spare USB-C cable that was bundled with a mobile phone. While the laptop successfully receives power from the monitor, the display resolution is restricted to 1080p at 30 Hz and the RAID storage array is not recognized by the operating system. Which of the following is the MOST likely cause of this issue?

  1. The bundled phone cable only contains USB 2.0 wiring and lacks the high-speed differential pin pairs required for DisplayPort Alternate Mode and SuperSpeed data.Answer
  2. B
    Physical USB Type-C ports cannot transmit native video signals without an active inline DVI-D conversion adapter.
  3. C
    USB Power Delivery over a single cable reduces available display bandwidth down to single-link video limits.
  4. D
    Thunderbolt 4 standards automatically disable integrated USB hub controllers whenever screen resolutions exceed 1080p.

Answer

The issue is caused by using a USB 2.0 phone charging cable that lacks the internal high-speed wiring required for DisplayPort Alternate Mode video and SuperSpeed data transmission.
Although USB Type-C uses a unified physical connector, individual cables vary significantly in their internal capabilities. Charging cables included with smartphones are wired only for USB Power Delivery and legacy USB 2.0 (480 Mbps) data lines. They lack the high-speed differential wire pairs required for DisplayPort Alternate Mode (video transport) and SuperSpeed USB data. Replacing the charging cable with a full-featured USB-C or Thunderbolt 4 cable restores native 4K at 60 Hz display output and enables the integrated USB hub for the RAID array.

Step-by-Step Solution

1
Analyze the physical cable rating and pin architecture.
Identified that the cable used is a basic USB-C charging cable intended for mobile devices.
Mobile charging cables omit high-speed data lanes to reduce costs and cable thickness, carrying only USB 2.0 D+/D- lines alongside power delivery wires.
2
Evaluate protocol requirements for 4K video and external storage.
DisplayPort Alternate Mode (for 4K @ 60 Hz) and USB 3.x data (for the RAID controller) require populated SuperSpeed lanes.
Without these high-speed physical wire pairs, the display cannot receive full resolution signals and connected USB 3.0/PCIe devices fail to enumerate.
3
Identify the proper resolution strategy.
Replace the charging cable with a full-featured USB-C (10Gbps/20Gbps) or Thunderbolt 4 cable.
Full-featured cables contain all necessary internal wiring to concurrently transmit high-resolution video, high-speed data, and power delivery.

Key Concept

USB Type-C Connector Form Factor vs. Protocol and Cable Specifications
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Topics

Display Cables and Connectors

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