While building a 1U Freenas server I had need of a couple custom IDE cables. I purchased a pair of Ultra Products rounded 80 conductor cables on December 07, 2007 at the Hoffman Estates Tiger Direct, planning to cut them open and re-crimp as needed. After cutting through the jacket and shielding I found I had been swindled.
The 40 extra conductors in an 80 conductor ATA cable are grounds designed to prevent crosstalk between the 40 data conductors. It is this reduction in crosstalk that allows data rates in excess of 33MB/s without introducing errors. In a flat cable, the grounds are simply interleaved between the data conductors. As the design of a rounded cable makes this interleaving impossible, quality rounded cables use twisted pairs, each consisting of one data and one ground conductor.
As seen in the pictures below, the Ultra Products cable claims to use twisted pairs, when it in fact does not. I have included pictures of a real twisted pair cable from A.C. Ryan for comparison.
