If you are using the 80 wire ATA 66/100 ribbon cable, they are CSEL or Cable Select arranged., The blue connector is to the controller . . . the gray to the slave and the black to the master. If you set all devices to CS, it is their position on the cable that determines their status.
Back in the 40 wire ribbon days, you had to have a specially prespared Cable Select ribbon in order to use the CS setting.
CS has some advantages . . . I have used it for almost 4 years now. It eleminates the problem of setting jumpers on IDE devices. For details see this site:
CSEL