Welcome to the IDE Question page of the Colour Classic Compendium

 

Welcome to

Colour Classic Compendium

Presented by Stuart Bell(stuartsmacs at dsl dot pipex dot com)

 



'The IDE

question'

 

 

  All trademarks, registered trademarks etc. etc. acknowledged.

This text and photographs (c) Stuart A Bell and Alexey Danilchenko 2001

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

Above: A standard IDE cable showing that the key 'bumps' are on the same side when the cable is folded (not twisted).

What's the question? Well you may ask! The issue is whether the description on the famous 'Takky' site of how to use an IDE drive with a Power Colour Classic is right, misleading, or just plain wrong.

It starts with the problem that, perhaps because Apple don't use the usual 'pin 1 is red' convention in their wiring loom, Takky has misnumbered the pins on his diagram. If you ignore his numbering but connect up an IDE device as he shows using the Apple loom, then you'll probably be OK. But if you try and relate his numbering to the IDE standard, or use a standard IDE cable, you could end up with problems.

I personally have never tried to use an IDE drive in any variety of CC, so this page is largely the work of Alexey Danilchenko, who has probably spent more time on this question than he would wish!

The confusion starts with the wiring loom:

Apple's wiring loom uses an IDE connector with the line to pin 40 coloured red.

Above: the IDE cable from the Apple wiring loom connected to an IDE CDROM drive. Pin 1 on the drive is nearest the power connectors on the right, but you can see that the red connector on the cable is pin 40!

 

The IDE standard is to make the line to pin 1 as red.

Above: a standard IDE cable connected to an IDE CDROM drive. Pin 1 on the drive is nearest the power connectors on the right, and you can see that the red commector on the cable is pin 1.

(There are also some non-standard IDE cables around, especially from older PCs, and there's a note to that effect at the bottom of this page, but to illustrate those would only cause more confusion!)

 

Alexey writes: "Initially for me the problem was not whether pin1 is red or not - there probably could be IDE cables without any red wire at all. The problem with the Takky diagram is that it just was not correct from the point of view of the IDE standard.

The IDE standard defines a 40 pin parallel connector (http://www.bbdsoft.com/ide.html) where pin 1 is "Reset IDE" signal and pin 40 is "Ground". This means that we undeniably have a pattern of pins which could not be reversed and the connection work. It's really easy to check that the connector that is labelled pin 1 on Takky's diagram (C11 connector of the main logic board connector) is actually connected to the ground, and so must be pin 40!

Now if someone tries to make an IDE cable on his own using flat cable without any red wire marking, then that person will have to connect the pins properly and by using Takky's diagram the ground signal will be actually connected to pin 1 of HDD IDE connector. It simply won't work."

The conclusion has to be that the pin numbering on the Takky diagram is wrong. So, if you use a standard IDE cable, the red connector should go to C50 on the main logic board connector. This is pin 1 on the IDE standard

And it's really easy to distinguish a standard IDE cable from a non-standard one. The rule is: if you combine two ends of IDE cable together (by folding cable in the middle) without twisting cable - so that their red stripes will be on the same side then key bumps on the connectors on a standard IDE cable should be oriented in the same direction. See photo on left. On a non-standard IDE cable they will be oriented in opposite directions.

Footnote from Alexey: I found (with a help of my IT administrator at work) that there used to be (and still may be) wrong IDE cables produced for some older PC motherboards. They have standard keyed IDE connectors to HDDs but the connector supposed to be attached to motherboard is reversed. Seems like it was done to prevent mistakes like "which IDE cable end connect to where?".

Unfortunately I was able to find only one cable of this type - and the one I had has key-bump on the motherboard (reversed) connector shaved off to fit in normal motherboards. All other IDE cables I was looking at in a shops were standard IDE cables.

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