Dell Latitude 3400 Service Manual page 10

Table of Contents

● Full-duplex data transfers and support for new transfer types

● Backward USB 2.0 compatibility

● New connectors and cable

The topics below cover some of the most commonly asked questions regarding USB 3.0/USB 3.1 Gen 1.

Speed

Currently, there are 3 speed modes defined by the latest USB 3.0/USB 3.1 Gen 1 specification. They are Super-Speed, Hi-Speed

and Full-Speed. The new SuperSpeed mode has a transfer rate of 4.8 Gbps. While the specification retains Hi-Speed, and

Full-Speed USB mode, commonly known as USB 2.0 and 1.1 respectively, the slower modes still operate at 480 Mbps and 12

Mbps respectively and are kept to maintain backward compatibility.

USB 3.0/USB 3.1 Gen 1 achieves the much higher performance by the technical changes below:

● An additional physical bus that is added in parallel with the existing USB 2.0 bus (refer to the picture below).

● USB 2.0 previously had four wires (power, ground, and a pair for differential data); USB 3.0/USB 3.1 Gen 1 adds four more

for two pairs of differential signals (receive and transmit) for a combined total of eight connections in the connectors and

cabling.

● USB 3.0/USB 3.1 Gen 1 utilizes the bidirectional data interface, rather than USB 2.0's half-duplex arrangement. This gives a

10-fold increase in theoretical bandwidth.

With today's ever increasing demands placed on data transfers with high-definition video content, terabyte storage devices,

high megapixel count digital cameras etc., USB 2.0 may not be fast enough. Furthermore, no USB 2.0 connection could ever

come close to the 480Mbps theoretical maximum throughput, making data transfer at around 320 Mbps (40 MB/s) — the

actual real-world maximum. Similarly, USB 3.0/USB 3.1 Gen 1 connections will never achieve 4.8Gbps. We will likely see a

real-world maximum rate of 400MB/s with overheads. At this speed, USB 3.0/USB 3.1 Gen 1 is a 10x improvement over USB

2.0.

Applications

USB 3.0/USB 3.1 Gen 1 opens up the laneways and provides more headroom for devices to deliver a better overall

experience. Where USB video was barely tolerable previously (both from a maximum resolution, latency, and video compression

perspective), it's easy to imagine that with 5-10 times the bandwidth available, USB video solutions should work that much

better. Single-link DVI requires almost 2Gbps throughput. Where 480Mbps was limiting, 5Gbps is more than promising. With its

promised 4.8Gbps speed, the standard will find its way into some products that previously weren't USB territory, like external

RAID storage systems.

Listed below are some of the available SuperSpeed USB 3.0/USB 3.1 Gen 1 products:

● External Desktop USB 3.0/USB 3.1 Gen 1 Hard Drives

● Portable USB 3.0/USB 3.1 Gen 1 Hard Drives

Technology and components

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