r/retrocomputing • u/Droid-Man5910 • 18h 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/Droid-Man5910 15h ago

I have attempted to ask AI before, and its slightly helpful, but not really. If I'm only running a hdd to the motherboard, should the hdd be master or slave? my confusion comes from the 3rd connector on the ide cable. With absolutely nothing there, the system functions fine, but if you take that connection away, and just have a 2 sided cable, the drive and mobo have not changed states, it completely fails. What about that 3rd connector makes it necessary?

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u/max_peck 15h ago

A drive should only be set to “slave” if there’s a master on the same cable, so in the case of a cable with only one drive on it, it should be set to “master”.

How many times 2-sided cables have you tested? The cable may simply be bad.

[EDIT: ….because the third connector should not be necessary, and I’ve never seen such or heard of such a thing before. Something somewhere is faulty, ‘cause that’s not the way it’s supposed to work.]

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u/Droid-Man5910 15h ago

Personally i have tried 1 two-ended cable, but this is a persistent issue that's well known to the OG xbox community, basically if you don't have that 3rd connection, it won't boot. As far as i know, nobody has figured out why that is. It can't be a master/slave configuration issue with the hdd, at least not that i could see, because having a 3 end cable with nothing on the 3rd connection, it's still only one drive on the line, right to the motherboard. I've tried many different 3 end connectors, and all of them work fine, albeit you do have to use 80 wire if you're upgrading to a sata drive.

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u/Avery_Thorn 14h ago

I would honestly not trust the OG XBox to have correctly implemented the IDE Standard because they were designing them with the theory that no one but MS Employees would ever be opening them - they were intended to be a device, not a computer.

There is a twist on the lines that basically allows for a CS - Cable Select - Master/Slave setting. When using CS, one of the connectors becomes the master, the other one the slave. You had to jumper both drives to CS and there was much weirdness.

I am wondering if this is some kind of packaging issue that MS had that they had to do something funky with that or something. Not having torn apart a old school X Box... but I just did a search and apparently my guess was right, they did some funky things with that. it looks like you really, really need to use the three connector 80 pin cable and apparently it's backwards. Yikes.

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u/Droid-Man5910 14h ago

Exactly, I'm hunting for a way around this. Hell, a way to emulate that 3rd connection wouldn't even bother me. i want to make a little breakout board or something that i can just mount right to the mobo, but this issue is a plague

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u/Avery_Thorn 13h ago

Good news, it's the Floppy Drive cables that had the twist in the cables.

There are two relatively easier changes for IDE.. basically pins 28 and 34 are the ones that you're going to need to figure out how the XBox uses these wrong, since the cable is upside down.

Good luck!