25 Apr
2018
25 Apr
'18
10:54 p.m.
On 4/24/18, Greg 'groggy' Lehey <grog(a)lemis.com> wrote:
Hmm. The earliest 3330s had 100 MB per disk, considerably more than
the 3340. I had thought that the 3340 had fewer surfaces. And the
3330s definitely only had one disk per unit, though they brought out
an 8-drive cabinet with a whopping 2.4 GB (by the time I used them).
The 3340 indeed had fewer platters per unit than the 3330, and because
of that a lower disk capacity. Both the 3330 and 3340 were CKD
format, not fixed-block, so the capacity depended on the record size.
Highest storage capacity was achieved with one record with a
zero-length key field covering the full track (called full-track
blocking).
According to the IBM Archives web page
(https://www-03.ibm.com/ibm/history/exhibits/storage/storage_3330.html)
the 3330 was code-named Merlin. It could have from 2 to 16 spindles
per controller. Originally each disk pack had a maximum capacity of
100 MB. The 3330 model 11 used IBM 3336 disk packs that had double
the original capacity (up to 200 MB).
This IBM Archives web page
(https://www-03.ibm.com/ibm/history/exhibits/storage/storage_3340.html)
says that the 3340 was code-named Winchester. This page reports, but
does not verify, the "30-30" Winchester rifle story. The IBM 3348
Data Module, the disk pack equivalent for the 3340, was a sealed
module that contained the head assembly. This reduced the hazards of
head misalignment and surface contamination. Unlike later
sealed-module disks, the 3348s were removable media. Modules with
maximum capacities of 35 MB or 70 MB were available. There was also a
70 MB module with up to 0.5 MB accessible from fixed heads.
-Paul W.