Examkin

Question

Difficulty: MediumNetwork and Peripheral Cables and Connectors

A system administrator connects an external NVMe SSD enclosure to a workstation host port labeled USB 3.2 Gen 2x2 (20 Gbps) using a USB Type-C cable that came bundled with a smartphone charger. During large file transfers, the administrator observes that throughput peaks at approximately 40 MB/s (480 Mbps). Which of the following is the most likely cause of this throughput limitation?

  1. A
    The USB Type-C connector was inserted in an inverted orientation, causing the host controller to default to USB 1.1 fallback mode.
  2. The bundled charging cable lacks the internal SuperSpeed data lanes required to transmit high-speed USB 3.2 data signals.Answer
  3. C
    USB Type-C cables require an active PCIe-to-SATA converter bridge built into the cable housing to exceed 5 Gbps throughput.
  4. D
    USB 3.2 Gen 2x2 specifications mandate the use of optical fiber cabling with ST connectors to achieve bandwidth above 10 Gbps.

Answer

The bundled charging cable lacks the internal SuperSpeed data lanes required to transmit high-speed USB 3.2 data signals.
While USB Type-C establishes the physical connector geometry, individual cable assemblies vary in internal pin wiring. Manufacturers commonly produce USB-C charging cables with only VBUS, GND, and USB 2.0 (D+/D-) conductors to keep cables thin, flexible, and inexpensive. Without the high-speed differential pairs (TX1/RX1 and TX2/RX2), the connection defaults to USB 2.0 High-Speed (480 Mbps / ~40 MB/s).

Step-by-Step Solution

1
Analyze the observed transfer speed
Peak throughput of ~40 MB/s corresponds directly to the 480 Mbps theoretical limit of USB 2.0 High-Speed.
Determining the exact transfer rate helps identify which legacy USB standard is actively operating.
2
Evaluate physical cable construction vs. protocol capabilities
Although the cable uses a physical USB Type-C form factor, charging cables frequently include only power conductors and USB 2.0 data lines (D+/D-).
The USB Type-C form factor specifies the physical connector shape, but actual data rate capabilities depend on the internal wiring of the specific cable.
3
Determine root cause
The missing SuperSpeed (TX/RX) wire pairs prevent the host controller and drive from negotiating USB 3.2 Gen 2x2 (20 Gbps) speeds, forcing a fallback to USB 2.0 speeds.
Full-featured USB-C cables require 4 pairs of SuperSpeed data lines to support dual-lane USB 3.2 Gen 2x2 operation.

Key Concept

Physical Connector Form Factor vs. Cable Wiring and Protocol Capabilities
Estimated Time:1m 0s
Rate this question

Topics

Network and Peripheral Cables and Connectors

More questions from this topic