Many of the first PCs in the mid 1980s were outfitted with hard drives that used PATA (an acronym for Parallel Advanced Technology Attachment) and IDE (an acronym for Integrated Drive Electronics) technology. As with all older devices back then, parallel transmission was the order of the day, allowing for very limited throughput. An easy way to identify older IDE drives is to simply have a look at the interface where the data and power cables connect to the drive.

These older drives, as seen in the following image, have four pins for power, which connect to a Molex connector, separated by eight pins used to set the device as a master or slave device, and then 40 pins for the IDE data cable, which transmits the data to the motherboard:

In 1994, advancements in technology led to the release of EIDE (an acronym for Enhanced Integrated Drive Electronics), which saw an increase in the number of pins for the data cable from 40 to 80, also increasing the transmission speeds from 4 Mbps to a possible 133 Mbps.

IDE/EIDE were still, however, limited to a maximum of four IDE/EIDE drives per computer, as the jumper pins on the drive only allowed for two primary and two secondary drives, set in a master and slave configuration. Consideration also had to be given to the fact that CD-ROM and RW devices and DVD-ROM and RW devices were also using IDE/EIDE technology at that time.