> On Jul 9, 2015, at 9:27 AM, P Gebhardt <p.gebha...@ymail.com> wrote:
>
>
>
>> I remember encountering them mostly as replacements for the terrible 821
>> drives, which had the appearance of an 808, but substantially increased
>> capacity. I don't think any 821s were ever installed at a customer's
>> site, however--I saw the lot of them that we had falling to the CE
>> sledgehammer.
>>
>> They were replaced by banks of 844s--lots of them. I think one site had
>> well over 100 installed, all hooked together with a MAC on at least 2
>> Cyber 74s.
>>
>>
>> --Chuck
>
>>
>
>
> Wow, more than hundred of these CDC drives??? This must have been a massive
>
> installation! I didn't know so many disk drives could be combined with
>
> Cyber systems. Thanks for the insights!
> I was already amazed by pictures provided by the University of Auckland:
>
> https://www.cs.auckland.ac.nz/historydisplays/FifthFloor/MagneticDataStorage/DataStorageImages/DiskPacks/CDCComputerRoom.jpg
>
> It doesn't say, though, where this picture was taken.
Wow. It isn’t clear how many systems are behind those drives.
And I thought CERL (University of Illinois PLATO) was a big setup. When I was
there (1975-1978) it had, I believe, about 20 844 drives. Those were all
connected to a single 7054 (via extenders of course, which aren’t well
documented in the manuals I have seen) and from there to a dual mainframe setup
(Cyber 73 and CDC 6500). Both mainframes would do I/O, and on each there were
two PPUs involved in the I/O to allow 1:1 interlace on 70-series channels.
This setup seriously exercised the drive reservation logic.
I ran into a controlware bug there, trying to use the Deadstart function
(03uu). It runs a sequence of conventional operations internally in the 7054,
but as supplied it did not correctly handle a drive interlock status and would
get things wedged up. That wasn’t hard to fix; it gave me my one exposure to
the controlware code, which is why I have a copy of it, though unfortunately
not a copy of the manual.
In theory, a 7054 with extenders can support 64 drives, since the unit number
is a 6-bit value. And also, again in theory, you could hook up multiple 7054s
if you need more drives than that. So well over a 100, accessible to a single
system, is at least theoretically possible.
Chuck, what (in this context) is a “MAC”?
paul
