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2311 Disk

You should look at disks in general and addressing.

The disk was fairly large with data on 10 surfaces. There were 200 cylinders. On the top the head assembly was marked 0 to 200 and had an index pointer. You could look down through the glass on top and watch the head go in and out. If you were reading the disk sequentially you could easily tell how far you were.

It only held a couple of meg, I think 7, but I could be wrong.

The heads on modern drives move with magnets. The 3211 used hydraulics to move the heads. One of our drives had a small leak and when IBM came in every week to do PM they would grab a handful of card chips and drop them in the bottom of the drive to soak up the oil.

When you powered the drive off it would spin down and when it stopped you opened the top and a piece came out and fit into the pack to keep it from moving as you screwed the top on. If you opened the top while it was still moving it made a noise from the piece trying to fit into the pack. The rumor was that if you kept it up the drive would break. You didn’t want to stand there for the minute it took to spin down so you would open the top, just a little so it would not make the horrible sound, and stick your hand in and over the side and touch the top of the pack so the friction with your finger tips would slow it down faster.

There were some buttons and lights on the drive, but the only thing i remember is the start button. It may have been a start/stop button or there was a start and stop, I don’t remember and whatever lights they had I don’t remember ever using them. There was probably a ready light, but you could see it spinning so the light was redundant.