Some weeks ago I was in a AIX forum where one of the members asked to know the difference between a 68pin SCSI hard drive and an 80pin one. So, what I did was to grab some of those hard drives I had sitting around and take a picture of their business end, i.e. where you can recognize which one is which.
If you look at the top hard drive, you will notice it has a large connector to the left and a power connector (the same one used in the old PATA drives) to the right. That would be a 68pin drive; if you want to count, there will be 68 pins on that large connector. Go ahead; I will wait. While you count, I will pass the time by saying some older UNIX workstations, such as the IBM RS6000 up to (as far as I know) P3, and the old DEC Alphas use those drives. The largest 68 pin drive I have ever seen is 32 (or is it 36?) GB.
By elimination, the two drives on the bottom are of the 80pin variety. As you can see, they have only one large connector right smack in the middle; power and signals go through that connector. And, it does have 80 pins. Sun workstations since the Sparc 20 vintage have been using these drives whenever they wanted SCSI. In addition to these workstations, they also find their way into some SANs. If you are looking to buy them, sometimes they go for the acronym SCA. I have personally seen 147GB SCA hard drives, but I do know there are 500GB ones out there.