[Simh] Which PDP-11 to choose

[Tim Wilkinson]

Back in 85 have had applications to purchase a 785 – 780-750-730 then 725 rejected, we were fortunately given a 750 by a sister company who were upgrading to a 785, but they took their disks. So we had to buy for ourselves.

 

To keep the bean counter happy we went for a System Industries controller and 4 super Eagles.

 

But back then there was a problem with the eagles and all 4 had to be swapped out 4 times.

 

Carrying them up stairs to the computer room was not fun. The platter size may have been reduced. But the weight!!!

 

Tim

From: Simh [mailto:simh-bounces at trailing-edge.com] On Behalf Of Clem Cole
Sent: 01 July 2019 14:08
To: Patrick Finnegan <pat at computer-refuge.org>
Cc: SIMH <simh at trailing-edge.com>
Subject: Re: [Simh] Which PDP-11 to choose

 

I can not say why it followed that naming convention, but it did.   The drives of that day were referred to as 19" technology since that's how they mounted.   FWIW:   Most manufacturers at the time used the same platter size as the original IBM 1311 (which as you pointed out was 14"), but not everyone, for instance, the Fujitsu Eagle used 10.5-inch platter.   FWIW:  I answered a bunch of this in: https://www.quora.com/How-do-hard-drives-get-smaller-and-smaller-in-size-bigger-and-bigger-in-capacity-every-year-when-the-fundamental-physical-processes-behind-them-do-not-change/answer/Clem-Cole 

 

On Mon, Jul 1, 2019 at 8:52 AM Patrick Finnegan <pat at computer-refuge.org <mailto:pat at computer-refuge.org> > wrote:

 

 

On Mon, Jul 1, 2019 at 7:32 AM Clem cole <clemc at ccc.com <mailto:clemc at ccc.com> > wrote:

19” form factor for the disks drive fir the space in the 19” relay rack.  You’re right the platters themselves were smaller.  The disks were referred too by the mechanical FF.  19, 8, 5.25 etc.   

 

But, 8" hard drives have 8" platters, and 5.25" hard drives have 5.25" platters. The casing on a the 5.25" drive in front of me is almost 6" wide. 

 

Pat



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