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Difficulty: MediumNetwork and Peripheral Cables and Connectors

A technician connects an external NVMe storage enclosure to a computer's USB-C port using an unbranded USB-C to USB-C cable found in an accessory drawer. Although both the enclosure and the motherboard port support USB 3.2 Gen 2 speeds up to 10 Gbps, file transfers consistently cap at approximately 40 MB/s (under 480 Mbps). What is the most likely cause of this performance bottleneck?

  1. The cable is a USB 2.0 charging cable that lacks the internal high-speed SuperSpeed data lanes.Answer
  2. B
    The host computer requires an active Thunderbolt 4 host controller to achieve speeds above 480 Mbps over USB-C.
  3. C
    High-speed video display bandwidth standards require the cable to be terminated with DB-9 serial connectors.
  4. D
    The cable internal wiring was terminated using the T568A wiring standard instead of the T568B standard.

Answer

The cable is a USB 2.0 charging cable that lacks the internal high-speed SuperSpeed data lanes.
The USB Type-C connector is a physical form factor. Cables manufactured primarily for device charging frequently omit the SuperSpeed differential signal pairs needed for USB 3.x, falling back to legacy USB 2.0 data throughput (~480 Mbps / ~40 MB/s real-world).

Step-by-Step Solution

1
Analyze the observed transfer speed bottleneck.
Transfers cap at ~40 MB/s, which corresponds directly to the theoretical 480 Mbps maximum of USB 2.0.
Identifying the transfer cap narrows down which protocol speed the connection has negotiated.
2
Evaluate the cable capabilities versus the physical connector form factor.
The physical USB-C form factor does not guarantee USB 3.x SuperSpeed wiring inside the cable assembly.
Many USB-C charging cables only incorporate power wires and legacy USB 2.0 D+/D- data lines to reduce manufacturing cost.
3
Determine the required resolution.
Replacing the cable with a rated USB 3.2 Gen 2 (10 Gbps) USB-C cable will enable full bandwidth.
Matching both the cable specifications and port standards allows SuperSpeed data lanes to function.

Key Concept

Physical USB-C Form Factor vs. Underlying Cable Protocol Capabilities
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Topics

Network and Peripheral Cables and Connectors

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