Got in the mood to take something apart today.

[HAL9000]

I was kinda bored today, so I had to take something apart. I noticed how everyone seems to comment that ATA66 cables have an extra 40 ground wires that "aren't connected to anything" so I had to check it out. Turns out that it couldn't be further from the truth and that there are a lot of interesting connections on that 80 wire cable.

Lets start with the extra 40 wires. they are connected to each other by means of a single plate through each the motherboard, slave, and master connectors. So they are just one big grounded mass down the entire line.

Starting at the motherboard, pins 2, 19, 22, 24, 26, 30, 34, and 40 are all grounded to the center plate, but pin 34 is not connected to the ribbon cable.

The next connector, the slave, has 2, 19, 22, 24, 26, 30, and 40 grounded to the center plate, 34 is not. It also is entirely missing pin 28, there is no physical connection to the hard drive.

The master on the end has 2, 19, 22, 24, 26, 30, and 40 grounded to the center plate just like the slave, but has a physical connection to pin 28.

Lastly, pin 20 is blocked out on all 3 connectors.

Yes, I was obviously bored today, but I figured those extra 40 wires had to be doing something somewhere or why would the controller card be able to distinguish between a 40 and 80 wire cable. I just thought that it might be an interesting piece of information to those that ask what is the difference between the 40 and 80 wire IDE cables.

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If it ain't broke, you're not pushing hard enough!

[Charliey]

That is interesting. You must have been really bored.

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-Charlie

[HAL9000]

I was, and I'm starting to collect a pile of ATA66 cables, so it was no real loss to take it apart. I've always had a bad habit of taking things apart. Gotta see what mysteries are inside, even if I don't fully understand them. Damn near sent my dad nuts during my teen years. He bought me my first car, a used 77 Pontiac Laurentian 4 door. That thing spent more time taken apart on the driveway than anything else, but what a sleeper. I could get 6 inches of air under the front tires (providing I got traction). Damn near gave dad a heart attack the first time that he drove it to the corner store http://www.pcmech.com/ubb/biggrin.gif

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If it ain't broke, you're not pushing hard enough!

[fred]

It is perhaps the fastest way to learn...to pull things apart. Well, er, that's what I told my dad when I pulled the Tv to pieces one day. http://www.pcmech.com/ubb/smile.gif He never did understand though. He just considered me to be a technical vandal. Toaster had exactly the same problem I believe...!! http://www.pcmech.com/ubb/smile.gif

[This message has been edited by fred (edited 05-27-2000).]

[LawyerRon]

Toaster, you've got way too much time on your hands!

Regarding the ATA66 cable, I believe I read somewhere that the extra 40 wires don't carry any data but are there to support the faster data transfer rate by reducing interference or provide some shielding in some way. I'm not a tech but am I close to being correct?

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"To speak ill of others is a dishonest way of praising ourselves"

[fordvan]

When electricity travels through a conductor (wire) there is a magnetic field generated around the wire. These magnetic fields constantly expand and collapse and induce a current into nearby wires. These currents can disrupt data flow through an unshielded wire. The ata66 cables have ground wires between each data wire to send the inducted current to ground and therefore not affecting the data conductors.

[Toaster]

I tell ya folks, the only way to learn is to learn by sheer force.
I dig for info and collect what info is available. Failing this, I take the law into my own hands and learn with "acceptable risk". This includes whooping out my trusty "scope" and other goodies to find the hidden "truth".
Iv`e been doing this for longer then I care to remember.
But man did I learn. Sure, I fried a few goodies in my day during the "quest" but in all cases it gave me "insight" as to why it does what it does.
When I dismantled the family TV, my dad gave an ultimatum. "It *WILL* work or it *WILL* hurt." Well, it worked and better then it did. Thats where it all began....and to this day...If I dont understand it..I will, even if a given device must meet it`s demise in doing so.

Life is risk....risk is life...risk life.