just learned about how ATA improved performance by switching from a 40-conductor cable to an 80-conductor cable and changing nothing else--they just now had ground conductors separating each of the signal conductors and that allowed them to double the speed
the actual connector itself just had 40 pins, the ground pin was just brought out to like 40 of the conductors
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it was an identical connector to the original 40-conductor cable, too, which meant you could use an 80-conductor cable with a low-speed IDE/ATA drive too, and the 40-conductor cable could be used for high-speed drives at reduced performance
in other words: put ground traces between your high speed signal traces! on pcbs, ribbon cables, and flat-flex alike