12 Apr
2024
12 Apr
'24
7:13 p.m.
On Apr 12, 2024, at 2:10 PM, Tom Gardner via cctalk
<cctalk(a)classiccmp.org> wrote:
Data Cell - Tape, Card or Disk?
I'm pretty sure the developers thought of the media of the IBM 2321 as tape
rather than cards, although the strips (of tape) were addressed as disk
drives (DASD) not tape.
Actually, they look like a disk. See the 2841 manual on Bitsavers (that's the
controller which drives 2311 disks as well as 2321 data cell devices). It says that each
strip has 100 tracks, read/written by a movable heads unit that has 20 heads on it, so 5
positions. And it shows the layout of each track, which is the conventions count/key/data
layout of 360 disk drives like the 2311. Yes, variable length "sectors",
you'd specify in the JCL what you wanted for blocksize of that particular file. If I
remember right, the block length could vary from one block to the next, which is pretty
wild. (Contrast with the EL-X8 disk drive, which also has variable length sectors, but
more limited: a choice of one of 5 possible sizes, chosen on a per-track basis when you
first write or format that track.) Apart from those, I only ever remember seeing fixed
size sectors, though the actual lengths might be strange -- like the CDC mainframe disks
with sectors of 322 12-bit words.
paul