7 Jun
2005
7 Jun
'05
6:24 p.m.
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>
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.
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.
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