Enhanced Integrated Drive Electronics (EIDE)

What is Enhanced Integrated Drive Electronics (EIDE)?

Enhanced Integrated Drive Electronics or EIDE refers to the standard of the storage device interface which is simply an improved version of the traditional IDE standard.

Technically, this particular interface comes with enhanced features and follows the ATA-1 standard.

It uses a special cable to connect the hard drives to the motherboard and support a data rate ranging from 4 MB/s to 16.6 MB/s.

Understanding Enhanced Integrated Drive Electronics (EIDE)

Understanding Enhanced Integrated Drive Electronics (EIDE)

Enhanced Integrated Drive Electronics is simply an extension of the traditional Integrated Drive Electronics or IDE interface standard.

This is used for similar purposes for connecting mass storage devices but supports much higher data rates in comparison to the original standard.

Developed by the Western Digital, this specific interface is used typically on computer systems that are IBM compatible and are known by different names such as:

However, these names of the interface can be pretty ambiguous because all these alternative names conform to the ATA standard known as Fast ATA or ATA 2.

This makes it quite reasonable to use the terms ATA 2, Fast ATA, and even Parallel ATA to be used synonymously for Enhanced IDE.

However, adding to the confusion is the fact that this particular interface can also be referred to as an ATA 3 standard.

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This is because the interface is very much similar to the ATA 2 standard in spite of the fact that it comes with some additional features.

For example, both these ATA standards 2 and 3 support the identical maximum data transfer rate with the only difference that the ATA 3 uses a 44 pin connector and offers SMART support as well.

However, leaving the confusion regarding its nomenclature aside, the Fast IDE interface standard typically acts as the means for the mass storage device and the computer system to communicate.

And, since this communication is in parallel, the transfer rate is much higher.

This particular interface standard typically supports four modes out of which Mode 4 is most common.

This is the particular mode that supports a transfer rate of up to 16.6 megabytes per second.

In addition to that, the Enhanced IDE interface also supports a new mode which is called the Ultra ATA, or ATA 3 which can transfer data at a rate of up to 33 megabytes per second.

In short, the Fast IDE really allows much quicker access to the hard drive and supports larger capacities, DMA, PIO along with a few specific functionalities of the special ATA packet interface known as Advanced Technology Application Programming Interface or ATAPI.

Still, in spite of all these benefits offered, this interface had a pretty small life expectancy and is not used today in the modern computers that need much faster rate to transfer data between the computer system and the devices connected to it.

Characteristics of EIDE

One of the main features of EIDE is it is faster. It also supports many data transfer modes such as Programmed Input Output or PIO mode 3 and 4 with a maximum transfer rate range of 11.1 and 16.7 megabytes per second respectively and with a minimum cycle time of 180 ns and 120 ns respectively.

Apart from that, it also supports DMA modes 1 and 2 and Ultra DMA mode over 2.

In addition to the above, the other notable characteristic features of Fast IDE are:

It also ensures low cost of operation on average because the EIDE hard disk of a particular capacity costs relatively less in comparison to a SCSI or Small Computer System Interface hard disk of the same capability.

Fast ATA, however, offers a lower performance in comparison to SCSI even in smaller capacities which is also the fundamental reason for the low cost of these specific hard disks.

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The primary reason for the low performance level of this particular interface standard is not for its difference in the technologies with SCSI but simply due to the fact that the interface is not paired with the best drives by the manufacturers.

Ideally, this particular factor results in a few specific consequences that hinders the performance of any Fast IDE drive on an average such as:

These are also significant reasons for the low capacity or range of the EIDE hard drives at any given moment in time in comparison to the SCSI hard drives.

This is true even if the available capacities of the two types of drives may overlap sometimes.

Typically, the Fast IDE hard drives may come with a capacity ranging between 4.2 GB and 40.9 GB, but in comparison, the SCSI hard drives typically come with a slightly higher capacity ranging between 4.3 GB and 50.1 GB.

Traditionally, most hard drives use a three-number CHS addressing or identifying code known as Cylinder Head, Sector, with or without any onboard electronics.

The special characteristic of the Parallel ATA drives is that it has an additional logical or linear block addressing or LBA mode included in it. Using this particular mode, the drive can recognize a segment on the hard disk.

Apart from all these characteristics, this specific interface possesses some other significant characteristics that affect its performance such as:

Moreover, the simplicity of the design of the interface standard results in lower command latency.

This means that these drives will respond to commands much quickly. In fact, these specific drives can return the first data packet sometimes even more quickly as compared to any SCSI model of the same capacity.

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However, in spite of all its useful characteristics, this specific interface is replaced by SATA or Serial Advanced Technology Attachment interface which is used by all computers today.

What Does the EIDE Cable Connect to?

The EIDE cable will connect to the hard disk drive mainly. This is because EIDE in particular is designed to be the standard electronic interface between a mass storage drive and the computer system.

Its enhancements allow it to support a hard disk that is even larger than 528 megabytes in capacity.

The flat ribbon style cable of high quality can also connect different devices other than hard disk drives such as:

How Many Drives Can EIDE Support?

It can support up to four devices. Typically, the EIDE comes with a 40-pin attachment which is enough to support as many as two primary and two secondary devices connected to it in combination such as CD ROMs, hard disk drives and others.

It is the design of the interface and the EIDE/IDE controllers as well as the design of the two large cables that support this because it allows connecting two devices to each.

However, adding more drives to it will add to its limitations resulting in serious drop in the performance level.

This is specifically because the EIDE drives are usually not designed to be the fastest drives available.

Therefore, this fact makes them much less than an ideal solution to add more drives and expect to have the best disk performance, higher performance computing and other tasks such as file servers.


On the whole, as you can see after reading this article, Enhanced Integrated Drive Electronic is pretty good for low-cost computer systems that come with just a couple of hard disks and one CD-ROM drive.

Apart from its characteristics, there are also a few specific limitations to EIDE which are also now known to you.