[SPAM] - Re: Simulated disk drive for RT-11? - Sending mail serverfound on relays.ordb.org

[Allison]

>
>Subject: Re: [SPAM] - Re: Simulated disk drive for RT-11? - Sending mail serverfound on relays.ordb.org
>   From: "Jerome H. Fine" <jhfinexgs2 at compsys.to>
>   Date: Tue, 07 Jun 2005 10:27:42 -0400
>     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>
> >Allison wrote:
>
>>>>On Jun 6 2005, 22:46, Allison wrote:
>>>    
>>>
>>>>Note there were differenet backplanes used in the BA23 those
>>>>that were compatable with uVAX-1, those that were uVAX-II
>>>>and the microPDP-11. Use the wrong one with the desired CPU
>>>>and bad results happen.
>>>>
>>>I've never seen more than one type of backplane in a BA23, and only one
>>>is listed in my manuals: H9278-A.  It's compatible with all of
>>>microPDP-11, uVAX-I and uVAX-II without so much as a jumper change.
>>>Are you thinking of something else?
>>>
>>No, I have a few too.  I have this thing for aquiring odd systems.
>>  
>>
>Jerome Fine replies:
>
>As far as I understand, a 22 bit PDP-11/23 and all
>PDP-11/73 systems use the same memory as the uVAX-I.
>That would seem to indicate that the same backplane
>can be used for either CPU in a BA23 box.  As for a
>uVAX-II, I can remember using the SAME box for BOTH
>a PDP-11/73 and a uVAX-II system at least 5 years ago.

There were Q22 and Q18.  

The CD side of the indicated backplanes were notably different.
It's my uderstanding the uVAX-1 had a special backplane to 
accomodate non-PMI memory and there were some power wiring 
differences that were dangerous to AB wired cards.

One BA23 I got has a Q22 with all slot pairs AB/CB wired Q22
in a serpentine pattern.

All three BA23s came from internal to DEC.


Allison