So, what's the difference, interface-wise, between SCSI and IDE/ATA?
I ordered a Gateway a long time ago and one of my options was to pick a SCSI 20GB HD. I chose that option. Later when I got into building/configuring my own hardware I opened her up. She had the HD running through a IDE cable to a PCI card. I don't know why. I eventually removed the card and put the HD directly into the IDE port on the motherboard, and had no problems whatsoever.
Does SCSI use the same plug as IDE, or did Gateway lie to me and give me a second IDE controller instead of a SCSI controller?
Nope completely different -
ATA - 40 pin and either 40 wires or later cables use 80 wires.
SATA - Small plug
SCSI - Latest uses either 68 pin, 68 pin high density or 80 pin SCA.
Big diff is max transfers speeds (best avail devices)-
Ultra ATA - 133Mbs
SATA II - 300Mbs
Ultra 640 SCSI - 640Mbs