> On Apr 12, 2024, at 2:10 PM, Tom Gardner via cctalk <cctalk@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
