The following is a sata3 data cable picture taken from wikipedia

enter image description here

There are 4 wires for each differential pair, and I guess the two silver-colored cables are grounds, and the two bronze-colored cables are differential pairs.

My question is, what's the benefit of using two ground cables instead of one?



1 Answer 1


Your picture actually shows four ground wires (two on each side of each of the signal pairs). On the SATA connector, the middle two wires are connected to a single pin, so the connector has three ground pins.

The reason for these four wires is complex (mostly to do with crosstalk); it is well explained here: Why do cables have multiple grounds?

  • \$\begingroup\$ Thanks @Paul. It seems that two main purposes were mentioned in that thread, i.e., to alleviate both impedance mismatching (causing reflection) and magnetic field overlap (causing crosstalk). \$\endgroup\$
    – bruin
    Aug 11, 2022 at 1:30
  • \$\begingroup\$ You are right, although mismatching could also have been solved in other ways. \$\endgroup\$
    – Paul
    Aug 11, 2022 at 12:30

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