When purchasing a PC today, you often see the specification of IDE or EIDE connectors for interfacing to storage devices. Pure IDE is the AT Attachment specification (ATA), and EIDE is the term used for AT Attachment 2 an effort to enhance the speed and capabilities of the original ATA.

Two vendors, Western Digital Corporation promotes a proposed standard called EIDE, and Seagate Technologies has proposed "Fast ATA" as alternatives to the ATA.

Some improvements over the ATA IDE proposed by Western Digital were:

1. increasing the accessable storage capacity beyond 528MB.
2. increasing the number of hard drives beyond 2.
3. increasing throughput (speed).
4. giving the ATA access to devices other than hard drives.

Before you get too excited, the EIDE proposal required a rewritten BIOS! That is to increase the capacity up to a total capacity of 8.4GB by changing the logical block Address to a 28-bit address. BIOS, in the old days, had a 63 sector per track, 1024 tracks, and 255 r/w heads for a total capacity of 8.4GB; however, the ATA/IDE did not allow addressing of the total BIOS limitation.

There are other problems relating to EIDE, but as time passed, they seem to have been overcome, and EIDE drive interfaces are now available with some systems. Probably, if your BIOS is 1994 or later, it has EIDE.

In fact, an ATA-3 has been undertaken as early as 1994, but I have no information on the effort. It is envisioned as being able to reach 20MB/s transfer of data.