Well not totally, there are 2 types fo IDE cables
Ultra DMA (80-Conductor) IDE/ATA Cables and the
original 40-conductor IDE cable
The newer cable can be treated the same way as a 40-conductor cable. Since it is of higher quality, it can be used in place of a 40-conductor cable in older systems without any issues. However, it does not directly replace a 40-conductor cable select cable. Note also that the 18" length restriction associated with the original 40-conductor cable.
I was tot he point where I was going to RMA it back thinking it was defective, till I read the setup guide a little more carefully.
My Hd's ran fine with the 40's but a newer cd drive that I bought would only work with the cables that were supplyed with it, which in turn were the 80 cabes ones.