Re: [COFF] Disk Technology was [Simh] Which PDP-11 to choose - COFF

1 Jul 2019

We really should take this off-list if you want to continue the discussion
as it has little to do with simh and more history (so I'm CCing the TUHS
COFF list.  I'll include simh for now, but if you reply please kill the
simh part).

 An Eagle or Eagle-II was a whole lot lighter (and physically smaller) than
an RP06 or RP07 (or an RM series drive for that matter). It is interesting
to hear you had problems with the Eagles.   They were generally considered
the best/most reliable of the day.   The SI controller on the Vax was less
so, although many of us in the UNIX community used them.

FWIW: I was accused of jinxing the 19" SMD Ampex drive by Masscomp's field
service team.   The story is we could never make the Ampex drives work
reliably at UCB (they were cheaper in bytes/$ than the Eagles at the
time).   When I was being recruited to Masscomp as I was leaving UCB, they
were trying to use Ampex as their high-end SMD drive with the Xylogic 440
controller, but had not (yet) had a failure. [Xylogic, like Masscomp, was
ex-DEC folks]. Anyway, I had mentioned @ UCB we had given up on the Ampex
drive on our Vaxen, and within 2 weeks of my starting to work darned near
all of them that Masscomp owned had failed.

PC (Paul Cantrell), tjt and I did eventually make them work but only after
we got Xylogic to redesign the 440 to be the 450 controllers and PC spend
hours with the microcode team on the error recovery logic.  Funny, the
450/Eagle combination (and later Xylogic 472 tape)  became the de rigor in
the UNIX community.

BTW: if Mark and the simh team is to ever to create a solid
Sun/Masscomp/Apollo simulator, they will need to emulate the Xylogic
controller family.   One more thing for the forever growing list of things
I'd like to do when I retire, but I think I still have the engineering
specs for them and PC and tjt are still to be found ;-)

On Mon, Jul 1, 2019 at 9:19 AM Tim Wilkinson &lt;tjw(a)twsoft.co.uk&gt; wrote:

...
  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@trailing-edge.com] *On Behalf Of *Clem
 Cole
 *Sent:* 01 July 2019 14:08
 *To:* Patrick Finnegan &lt;pat(a)computer-refuge.org&gt;
 *Cc:* SIMH &lt;simh(a)trailing-edge.com&gt;
 *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-bi…

 On Mon, Jul 1, 2019 at 8:52 AM Patrick Finnegan &lt;pat(a)computer-refuge.org&gt;
 wrote:

 On Mon, Jul 1, 2019 at 7:32 AM Clem cole &lt;clemc(a)ccc.com&gt; 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

<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
Virus-free.
 www.avast.com

<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
 <#m_1729574511750107707_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>