Thread: IDE cables
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Old 21st March, 2002, 07:31 PM
Aedan Aedan is offline
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Join Date: September 2001
Location: Europe
Posts: 13,075

Originally posted by Kaitain
Twisted pair cables are arranged with current flowing in opposite directions (so the +ve and -ve of each connection would be twisted as a pair). Thus the EM-fields surrounding each wire in the pair oppose and cancel, preventing crosstalk.

My guess is that rounded IDE cables do a similar thing with signal and ground.
It'd be nice if it did, but it doesn't! As you correctly point out, twisted pair works by having mutually opposing current flows. Any common mode noise (noise of same amplitude on both lines) gets cancelled out when the two signals are subtracted from each other.

Unfortunately, to do this on an IDE cable would require a seperate ground wire from the IDE interface chips on the drive to the IDE interface chips on the mobo, meaning a 66pin connector would be needed. This would allow for the ground return. Alas, the hard disk connector only has 40 pins, so there's no way that the hard disk can set up a dedicated ground return for each signal.

Serial ATA will help in as much as it'll reduce things down to twisted pair communications without the need to sync up so many bits.

Any views, thoughts and opinions are entirely my own. They don't necessarily represent those of my employer (BlackBerry).
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