Simulated disk drive for RT-11?

[Jerome H. Fine]

 >Allison wrote:

>>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.
>
Jerome Fine replies:

That would explain the situation since no one else seems
to have ever seen a pure Q22 backplane for a BA23.

Since I can use a BA23 box with a PDP-11/73 with BOTH
normal memory below the CPU and PMI memory above the
CPU (actually, it can even be the same memory), the
uVAX-I should also be able to do so as well.  However,
for a pure Q22 backplane will all slots wired AB /AB
(I presume that is what you really meant to write),
PMI memory would not be possible for the PDP-11/83.
I presume that would also preclude a uVAX-II which I
assume also needs AB / CD slots as well.

On the other hand, if all the slots were wired as
AB / CD as in an BA213 box (is BA213 correct - that
would be for a uVAX-III) which has only AB / CD, the
PDP-11/73 should also work along with the PDP-11/83
although I have never hear of anyone using these
boxes for PDP-11 CPUs since they require different
boards which likely are not available to be used with
the PDP-11 in most cases.  Tony, do you have a UVAX-III
box or can anyone else comment?

Note that a BA11-S box is a 22 bit 4 * 9 backplane and
wired AB / CD for all 9 Qbus slots.  One of these years
I will try using a PDP-11/83 and PMI memory to test
the situation.

Sincerely yours,

Jerome Fine
--
If you attempted to send a reply and the original e-mail
address has been discontinued due a high volume of junk
e-mail, then the semi-permanent e-mail address can be
obtained by replacing the four characters preceding the
'at' with the four digits of the current year.