40 conductor is the original ide cable, that cannot support high speed data transfers. 80 conductor cable still has 40 connectors, but each of the 40 conductors are paired with 40 ground conductors. this elminates cross talk and interferance between data lines, and still allow you to use the cable in the same 40 conductor connector.
80 conductor cables allow you to connect you hard disks at 66 Mbps (Ultra ATA/66) or even 100 Mbps (Ultra ATA/100) transfer speeds, provided your drive supports them.
its always better to use 80 conductor cable even for 33 Mb or slower transfers (for older hard drives), since these cable can offer slight performance improvemnt.
beware, 80 conductors stuffed in a space where there were 40, these cables are very delicate.
girish
<font color=blue>die-hard fans don't have heat-sinks!</font color=blue>