From the earliest days of personal computing, direct cable connection was the most popular way to transfer data...
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from one PC to another.
Today, computers equipped with a network card and using straight-through or crossover network cables are able to transfer data at speeds much greater than what's possible with a serial or parallel cable. However, there are still times where we require a transfer via the serial or parallel port, and that's why it's important to understand direct cable connection.
Transferring data between computers via a direct cable connection can be performed using the following methods:
- Serial crossover cable;
- Parallel cable -- also known as Laplink cables;
- USB transfer or data link cable; and
- UTP crossover or straight-through cable.
Speeds depend on the transfer method selected; however, each method has specific requirements.
Direct transfer via serial crossover cables requires the existence of one free serial port on both the source and destination computer. Furthermore, the maximum attainable speed for data transfer via a serial port is only 14 Kbps -- 0.014 Mbps -- making it unpractical and extremely slow for large file transfers. Apart from the very low speed rates, most laptops, workstations and servers do not offer a serial port anymore, as the port has become obsolete and has been replaced by USB ports.
Transferring data via a parallel port is more practical, compared with a serial port, thanks to the greater speed rates of up to 1.1 MBps or 8.8 Mbps. However, as with serial ports, parallel ports are almost nonexistent, as they too have been replaced by USB interfaces.
Data transfers via USB ports are more popular; however, a special USB transfer cable -- or USB data link -- is required. Users cannot employ a standard USB cable used to connect printers or other USB devices. The special USB transfer cable contains electronic circuits that allow two USB ports to connect and transfer files.
USB speed transfers depend on the USB port version on the machines. The USB v1.1 specification provides a maximum of 12 Mbps, while the USB v2.0 specification increases throughput to 480 Mbps -- almost five times the speed of a 100 Mbps network. USB 3.0 and USB 3.1 boost throughput to almost 5 Gbps.
UTP crossover and straight-through cables are the final method of direct cable connection covered here. They also happen to be the most popular. Crossover cables are required for older network cards that do not support Auto-MDIX, while newer and gigabit network cards support Auto-MDIX and require simple straight-through cables. The supported transfer speeds are 10 Mbps, 100 Mbps and 1 Gbps, surpassing USB v2.0 transfer speeds by more than two times.
Installing Windows programs or components to transfer data is out of this tutorial's scope. Read about what you should check before attempting a direct cable connection.
Cabling series, lesson 8: Serial direct cable connection
Cabling series, lesson 9: Parallel direct cable connection
Cabling series, lesson 10: USB direct cable connection
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Chris Partsenidis asks:
Do you still use direct cable connections for data and file transfers? If so, what for?
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