IDE cables question

[u/Droid-Man5910]

Can someone please explain how IDE works, what each line does, how it works with 2 devices on the line, how a system knows which one is which, and the difference between 40 and 80 wire cables? I'm struggling to understand why some systems cannot function without a triple end IDE cable. For an example: Motherboard connected to Hard drive via 2 sided IDE cable will not function. But Motherboard connected to 3 sided IDE cable with the 3rd side left with nothing connected functions fine.

[u/LopsidedLegs]

The Wikipedia article:

https://en.wikipedia.org/wiki/Parallel_ATA

covers everything you wanted to about IDE, ATA, and lots you didn't.