Direct Cable Connection

From the early PC days, Direct Cable Connection (DCC) was the most popular way to transfer data from one PC to another. Of course, it might seem a bit of an "old fashioned" way to transfer data these days but remember that back then most PC's were running Dos 6.22 or Windows for Workgroups 3.11 if you were lucky!

Today, all computers are equipped with a network card and using straight-thru or cross-over network cables, we are able to quickly transfer data at speeds much greater than a serial or parallel cable. However , there are still times where we require a transfer via the serial or parallel port, and that's what this page is about.

Transferring data between computers via direct cable connections can be performed using the following methods:

• Serial Cross-over cable
• Parallel cable – also known as ‘LapLink’ cables
• USB Transfer or Data Link cable
• UTP Cross-over or Straight-thru cable

Different speed rates are achieved depending on the transfer method selected, however there are some requirements for each.

Direct transfer via Serial cross-over cables require the existence of one free serial port on both source and destination computer. Furthermore, the maximum attainable speed for data transfer via a serial port is only 14 kb/sec (0.014Mbps), 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 since the introduction of USB ports.

Transferring data via a parallel port is more practical as opposed to a serial port thanks to the greater speed rates of up to 1.1 Mb/sec (8.8Mbps), however just like serial ports, parallel ports are almost non-existent as they too have been replaced by USB interfaces.

Data transfers via USB ports are a more popular solution, however a special USB Transfer (or USB Data Link) cable is required. Users cannot use a standard USB cable used to connect printers or other USB devices. The special USB Transfer cable contains electronic circuits allowing two USB ports to connect and transfer files.

Speed transfers with USB vary depending on the USB port version on the machines. USB v1.1 specification provides a maximum of 12Mbps while the USB v2.0 specification further increases this figure to 480Mbps, almost 5 times the speed of a 100Mbps network. USB 3.0 and USB 3.1 support speeds close to 10 times that of USB v2.0 however data transfer cables beyond the v2.0 specification do not exist or are extremely difficult to find.

UTP Cross-over & Straight-thru cables is the final method covered and happens to also be the most popular. Cross-over 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-thru cables. Transfer speeds supported are 10Mbps, 100Mbps and 1Gbps (1000Mbps), surpassing USB v2.0 transfer speeds by more than two times.

We will also be learning how to create the cables required to meet our goals and comparing the speed of the two (Serial and Parallel)

In the next pages, we’ll analyze Serial - Parallel ports and connection cables, and then move to USB ports & Data Transfer Cables.