Peripheral Cables - CompTIA A+ 220-1201 - 3.2

Understanding USB Technology and Its Evolution

Introduction to USB

• USB, or Universal Serial Bus, is the standard connection type for various peripheral devices like keyboards and mice.

• The first version of USB was 1.1, which operated at two speeds: low speed (1.5 Mbps) and full speed (12 Mbps). Cable lengths were typically 3 meters for low speed and 5 meters for full speed.

Advancements in USB Versions

• USB 2.0 significantly improved throughput with a maximum of 480 Mbps over a cable length of approximately 5 meters.

• USB 3.0 introduced "super speed" capabilities, operating at 5 Gbps over roughly a 3-meter cable; specifications do not define exact lengths but suggest practical limits for performance.

• Subsequent updates include USB 3.1 (10 Gbps) and USB 3.2 (20 Gbps), showcasing continued advancements in data transfer rates.

Connector Types Over Time

• Common connector types have evolved:

• Standard-A plug remains widely used.

• Standard-B plug is often found on printers and external devices.

• Mini-B and Micro-B plugs are typical for mobile devices.

• The introduction of the updated Standard-B plug for USB 3.0 features a taller design, while the Micro-B plug has undergone significant changes compared to earlier versions.

The Shift to USB-C

• To address the variety of connectors, the standardized USB-C connector was developed, allowing connections without worrying about orientation compatibility. This connector can replace all previous types but does not dictate signal type transmitted through it.

• Size comparisons show that the USB-C plug is similar to Micro-B but distinct from Standard-A plugs, indicating its versatility in modern applications.

Legacy Connections: Serial Cables

• Before USB became prevalent, serial cables were commonly used with various styles such as DB-9 and DB-25 connectors; these refer to pin counts rather than size alone (DB vs DE).

• RS-232 has been a long-standing standard since 1969 for transmitting serial information via these cables; they were essential before standardized connections like USB existed for peripherals like modems and keyboards.

Current Use Cases for Serial Connections

• Today’s use of DB-9 connectors typically involves legacy equipment such as older switches or routers where console ports are accessed via serial interfaces instead of modern connections like Ethernet or direct USB links.(272)

• Adapters are often necessary to connect newer systems using USB-C to older DB-9 interfaces when configuring network devices through their console ports.(310)

Connecting Peripheral Devices: Thunderbolt Technology

Overview of Connection Methods

• The RJ45 connector is used for console connections, while Thunderbolt serves as a high-speed serial connection that combines data and power in one cable.

• Thunderbolt's early versions utilized the Mini DisplayPort connector, allowing two channels of throughput at 10 gigabits per second each, totaling 20 gigabits for Thunderbolt version 1.

Advancements in Thunderbolt Versions

• Thunderbolt 2 enhanced throughput to 20 gigabits by aggregating channels but continued using the Mini DisplayPort connector.

• Modern devices now use USB-C connectors with Thunderbolt 3, which offers an impressive aggregated throughput of 40 gigabits and supports a maximum cable length of 3 meters for copper cables.

Daisy Chaining and Connectivity Features

• Thunderbolt technology allows daisy chaining of devices; for example, connecting a computer to a monitor, then linking that monitor to another monitor or external storage device.

• The system intelligently recognizes connected devices in the chain, ensuring efficient data transfer between them.

Enhancements in Thunderbolt 4

• The latest standard, Thunderbolt 4, maintains the same aggregated throughput of 40 gigabits but improves video output capabilities to support dual-4K displays and increases bandwidth to the PCI Express bus.