|If you use good lighting, you can usually see what position the jumper is set to at the back of the drive - e.g. M, S, C or CS, for Master, Slave, Cable Select. That may be merely etched into the plastic rather than printed in ink. |
Either one should be set to Master, the other to Slave, or both should be set to Cable Select.
It makes absolutely no difference which is set to which of those, or whether there is another drive on the same data cable, or an IDE hard drive on the same data cable, or which IDE header you connect to, unless you have an extremely old main chipset . The cpu accesses the drives one at a time - each drive is able to achieve it's own maximum speed .
It's NOT recommended you set one drive to Cable Select, the other to Master or Slave on the same data cable, because some combinations work, some DO NOT.