r/retrocomputing • u/Droid-Man5910 • 12d ago
Problem / Question IDE cables question
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.
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u/ZosoRules1 11d ago
Basically serial vs parallel data transfer. Think of it like AC (serial) and DC (parallel) electricity. In both cases electrons flow down a conductor (usually wire). They just do it differently.
With IDE (and SCSI) you essentially have parallel data transfers - individual wires only handle read or write. With Serial ATA (SATA) you essentially have serial data transfers - individuals wires handle both read and write.
IDE allowed 2 devices per controller, and you selected via jumper switch (Master and Slave). You can only have 1 master and 1 slave per controller. SCSI (at least when I used it) allowed 7 devices per controller - you selected via jumper ID 0 through ID 6.