1 Oct
2024
1 Oct
'24
11:55 p.m.
On 10/1/24 18:29, Tom Gardner via cctalk wrote:
I wouldn't call the 2314 low tech - it was the highest areal density at the time, a
breakthru with ferrite heads and very low cost to manufacture. Note I said cost, its
profit margin was enormous, in part by putting as much expensive electronics as possible
in the control unit. 😊
Actually the 2314 did not ship with the first 360's in 1965; it was announced in
April 1965 about 1 year after the 360 announcement and AFAICT from Bitsavers document
dates it didn't ship until late 1966, which FWIW, at the Computer History Museum, 1966
is also the date for first shipment of the 2414 and its ferrite heads. BTW the hydraulic
actuator design goes back to the 1311 - more or less the same actuator in the 1311, 2311
and 2314.
Well, yes, and in the days of SLT logic, everything was
expensive. So, putting as much of the functions in the
control unit rather than the drive was good. But, one thing
that this mindset caused was that they could not have one
drive seeking while another drive was transferring. The
entire operation, cylinder seek, rotational seek and data
transfer was all one atomic operation. That really killed
the throughput of the whole disk system. The reason was
that the IBM developers came from systems like 7070 and 7090
where all permanent storage was on tape, and they didn't
quite "get" how central disks were going to be to the 360
systems. They had the CKD scheme, where you could search
several cylinders for a match of some arbitrary field in the
DATA portion of a sector, but this resulted in massive
slowdown of the system, as it tied up not only the drive,
but the controller and the channel as well! Thus the need
for the database system, which would make selecting the
desired record much faster.
I didn't mean that the 2314 DISK was low tech, just that the
drive, itself, was quite spartan.
Jon