Ultra66/100 cable confusion

[HAL9000]

OK, bored at work today, so I decided to map out exactly what makes the blue, grey, and black connectors on an ultra cable unique and here is what I have. All cables run straight through with the following exceptions.

Blue Connector;

-Pins 2, 19, 22, 24, 26, 30, 34, and 40 are all commonly connected to the 40 ground wires.

-Pin 34 is connected to the ground wires, but is NOT physically connected to the cable.

Grey Connector;

-Pins 2, 19, 22, 24, 26, 30, 40 are all commonly connected to the 40 ground wires.

-Pin 28 has no connection to anything at all.

Black Connector;

-Pins 2, 19, 22, 24, 26, 30, 40 are all commonly connected to the 40 ground wires.

-All 40 data wires are connected.

So, how does each one become unique, it all seems to come down pins 28 and 34. The motherboard connection (blue) and the master drive connection (black) have a data wire connected to pin 28, where the slave drive (grey) does not. If it were only this difference, one should be able to reverse the cable to accomodate certain cable routing situations, but, there is pin 34 which is connected to the ground wires on all three connectors, but the data wire for pin 34 is only connected to the motherboard and slave, not the master drive. This is where things get screwed up if you try to reverse the cable as you now have an incorrect connection sequence.

Hopefully this has shed a bit more light on the ultra cable connection and not created more confusion.

[Toaster]

Keep in mind the following when dealing with EIDE/IDE devices in a "master/slave" combination.
In the beginning of IDE which was pioneered by Compaqs own in house drive manufacturing facility (Connor Peripherals) among other manufacturers, is that the IDE device is a BIOS device interface meaning it must be serviced via BIOS calls. This is the reason why your system requires a drive to be represented with a "drive type".
This dates back to MFM/RLL/ESDI and removable media devices such as floppy drives. Still, EIDE has roots in the ST506 interface presented by Seagate with the introduction of the ST506 MFM hard-disk and a whopping 5MB of user memory.
(rotating memory array is the technical term)
(in the years of the MFM/RLL drives of Seagate manufacture, all drives were sold using maximum UNFORMATTED capacity. IE: ST506 6MB of unformatted capacity)
Drive makers needed an interface that was cheaper and could outperform MFM drives of the day. The first few implementations of IDE was propriatory to Compaq and data rates rarely exceeded 750KB/sec.
When to ATA compliant hard disks are used on the same channel, one of the drives "interfaces" is unused and only the drive logic is used while the "master" does all the work. This was the reason why IDE had problems in the early years due to incompatabilities.