On Sat, 07 Mar 2020 08:39:47 +0000, Jan Panteltje wrote:

> In the eighties you had IBM drives of maybe it was 10GB? tha thad a
> mechanical lever likething on the side, it ws connected to teh head
> movement,
> If the head positioning got stuck or something you could move that lever
> and the thing would work again....
> So, anyways, sorry about that.
>
Wash your mouth out! Back in the '70s IBM was the Great Satan, with
predatory salesmen and SEs, all in the dark suit, white shirt and blue
tie company uniform and many brainwashed to the point of disbelieving
that anybody other than IBM even made computers. Yes, I did meet, and
worked with, a guy who had bought (gasp!) 3rd party disk drives and
consequently had a posse of IBMers show up and harangue his management to
try and get him fired.

Anyway - when I started work with ICL in the late 60s, our biggest disks
were 8 MB. The drives were desk height, about 50cm X 80cm on top. They
used removable cartridges with a stack of 10 recording surfaces, all 14"
diameter. Spun at 2800 rpm and had an average access time of around 135
mS.

By 1973 they'd grown to 60MB capacity and 20 recording surfaces, still
using 14" platters, spun a bit faster (3600 rpm IIRC) and access time was
down a little to under 100 mS. George 3 used a clever head movement
scheduler that tripled the effective access rate.

Biggest drive I ever saw back in the day was 400MB, still using 14"
removable cartridges, but the number of recording surfaces had more than
doubled.

FWIW, I first saw a microcomputer in 1976/77 at The Computer Store in NYC
at 5th and 35th, which sold SWTPC and Imsai systems, No disks of any sort
- they weren't around much before the early late 70s when Shugart 5.25"
floppies started to appear and then in the early 80s 5" hard drives with
(gasp!) 5MB or even 10MB capacity started to appear.


--
Martin    | martin at
Gregorie  | gregorie dot org

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