Simulated disk drive for RT-11?

[Allison]

>
>Subject: Re: Simulated disk drive for RT-11?
>   From: "Jerome H. Fine" <jhfinexgs2 at compsys.to>
>   Date: Tue, 07 Jun 2005 20:37:27 -0400
>     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>
> >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.

It's possible, I've done it and it fits well.  The Q22
18slot (M9275) is a nice backplane for non-PMI based 
systems. 


>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),

Yep.

>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.

Yes to that 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

Yes and mVII as well.  Though you forget the AB/CD, 
AB/AB mix of the BA123.

>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?

Never saw a BA213 with a other than a uVAX.

>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. 

M9275 18 AB slots (ab/ab), M9276 9ab/cb slots.

That works.  However I have BA-11S and BA11Ns with a mix of 
oddball non standard backplanes of my doing.  Most are the 
H9275 type and do watch the backplane jumpers.  The BA11N
boxes are actually hybrids of 11S and  

I only do Qbus 11s.  I have:

 H11 KD11-L in Heath backplane with serial and 16k ram
 11/2 KD-11 (with eis/fis)in H9281-AB 8slot AB (dual width)
 11/23 KDF-11 on 9281-AC 12slot AB 
    (11/23 overclocked, (4)8059 256kram, DLV11J, RQDX3, RX33, RD52, 
     VK170/LK02)
 11/23 KDF-11A in a BA11VA
 11/23 KDF-11B in a modded BA-11S
 11/23 KDF-11B with Hardware FPU (M8189) in BA-11S
 11/73 KDJ-11A in modded BA-11N

 Never mind having at least one of every backplane used for Qbus
 11s in BA-11 or BA23.

Allison