ATA 66 cable has 80 wires, 40 of them are ground wires. This is to reduce cross-talking. The ATA66 cable must be used to benefit the ATA66 speed, and also the motherboard must support it. ATA66 hard drives are backwards compatible though so if something doesn' t work, it will resort to the ATA33 speed. Just my 2 cents, from what I have learned. Susan Stubbs Which is it the difference between a cable ATA66 and ATA33? I refer to the physical differences of the cable. Thank you. [log in to unmask] www.colormar.com PCBUILD's List Owner's: Bob Wright<[log in to unmask]> Drew Dunn<[log in to unmask]>