Actually the Capacity Limit on drives 99% of the time locks them to 2.1GB, not the machines limit.
It wouldn't matter if the drives were Master, Slave or Cable select if they are on their own cable as they would still work fine, you just have to make sure you never have 2 drives set to the same thing on the same cable. On cable select, the middle connector is Master and the end one is Slave. The machine wouldn't be slower on the same IDE cable, infact you probably would never notice unless it is a very, very old machine that requires both drives to be locked to the same speed on the same cable (and I am talking like 486 era).
