Summary
Highlights
USB (Universal Serial Bus) has become the standard connection for many computer peripherals. USB 1.1 offered low speed (1.5 Mbps) and full speed (12 Mbps) over cables up to 3-5 meters. USB 2.0 significantly improved throughput to 480 Mbps over 5-meter cables. USB 3.0, known as SuperSpeed, provides 5 Gbps over 3-meter cables. Subsequent updates, USB 3.1 and USB 3.2, further increased speeds to 10 Gbps and 20 Gbps, respectively.
Early USB 1.1 and 2.0 utilized Standard-A, Standard-B, Mini-B, and Micro-B plugs. USB 3.0 introduced updated versions of the Standard-A, Standard-B (taller), and a significantly different Micro-B connector. The proliferation of various connector types led to the development of USB-C, a standardized, reversible connector designed to replace previous types and capable of carrying different signal types.
Before USB, serial cables were common, with popular types being the DB-9 and DB-25. These connectors are named for their size and number of pins (though DB-9 is technically a DE-9). They use the RS-232 standard for serial communication, established in 1969. While largely replaced by USB for modern peripherals, DB-9 connectors are still used for legacy equipment like older switches and routers, often requiring USB-to-serial adapters for modern computers.
Thunderbolt is a high-speed serial connection that carries both data and power. Early versions, Thunderbolt 1 and 2, used the Mini DisplayPort connector, offering 20 Gbps total throughput across two aggregated 10 Gbps channels. Modern Thunderbolt 3 adopted the USB-C connector, providing 40 Gbps aggregated throughput. Thunderbolt 3 supports copper cables up to 3 meters and optical cables up to 60 meters, and allows for daisy-chaining multiple devices. Thunderbolt 4 maintains 40 Gbps but enhances video output to support dual-4K displays and increases bandwidth to the PCIe bus.