On the old 40 wire 40 pin IDE cables it doesn't matter.
On the new 80 wire 40 pin I don't think it matters unless you set the jumpers to cable select. Then it's master at the end slave in the middle. The drive will probably work better set up as master when it's on one channel bye itself.
You can set it as a slave drive and attach it using the middle connector. It should be ok as long as it is not on the primary ide channel and even then it might be ok on some boards.