25 Oct
2013
25 Oct
'13
4:23 a.m.
azd30 wrote:
Hi,
I recently aquired an old Netcom system and I'd like to find out a bit more info about
this backplane.
It's an 11/23 system (based on CPU) . It has some standard DEC
cards in it (M8186 CPU, DLV11, BDV11 bootstrap board ) as well as a thrid party 256Kb
memory board and an MXV22 floppy controller.
Apparently the system ran RT-11 from floppies a few years back before it was put in
storage.
If you can specify all the boards (or at least the DEC boards) by their
board number (i.e. M8186), it would be more useful. Is the DLV11
an M8043 (actually DLV11-J)? Just in Case, please also mention
dual or quad board.
I have read through the PUPS archives, esp. a post from
Michael Sokolov back in 98, where he describes
the different types of QBus'es. Q/Q, Q/CD etc. Have also read through the info on
hampage.hu and various other sites that host PDP11 related info,
but am still unsure about this particular beast.
It looks like the backplane that I have (according to the archives and some documents
written at SLAC in late 70's)
is a serpentine or sinusoidal type configuration. The SLAC documents actually refer to the
Netcom backplane but they
describe it a simple serpentine type.
A diagram on my cardcage describes it as follows:
A B C D
------------>
<-----------
------------->
<------------
There is also a blurb about slot 2/CD being wired differently. Two slots on the diagram
are pre-printed for RL controllers. I can't rembeber the exact wording, since I
don't have the computer in front of me.
This is possible, but seems VERY unlikely with just
a 4 slot backplane. As far as I understand, in order
to be useful to support an RL controller, at least 2 slots
must be wired as ABCD. The BA23 box has the first
three slots as ABCD and the other five slots as ABAB,
so the concept is possible. Having two ABCD slots also
supports PMI memory with the memory being placed in
slot 1 and the CPU in slot 2, but that requires at least
a quad M8190 CPU card.
It gather that I insert the CPU in 1AB, then rather
than putting the next card in 2AB, I would place it in 1CD. Next would be 2CD and so on
,snaking down the line. Is this correct? While this is all fine for dual cards, but how
does this configuration
handle quad cards? I'm guessing that it has to do something with that 'blurb',
but that would mean that I can only have one quad card installed, and it would be right
towards the begining of the bus. The BDV11 should
be the last card in the chain from what I can remember.
I forgot to add, please also specify where all the current
cards are located in the back plane.
With an M8186 to start, the BDAL17-20 lines should be
either unconnected (for an 18 bit backplane) or ONLY
connected to each other (for a 22 bit backplane). If they
are unconnected, installing connections should convert to
a 22 bit backplane and you M8186 should be able to
access as much memory as you are able to place in the
backplane (up to 4 MB of course). At one point, a VT103
backplane was upgraded to 22 bits and a 4 MB memory
board installed.
Also, my CPU card is a rev. D so it can do 22bit
addressing. I'd like (if possible) to run 22bits, since this would allow
me at a later time to put in a 11/73 cpu that would give me more flexibility in what
OS's i can install on the machine.
I'll have to check if the backplane is wired for 22bits or not. I seem to remeber the
standard qbuses had the W1-W4 pins (?)
that you could wirewrap to change from 18to22 (i'm assuming that this operation
propagated the BDAL17-20 from slot 1 to the other slots) but this backplane has nothing
like that.
I'm planning on checking it with an ohmmeter, and it should be very obvious if these
signals are present across slots.
The backplane is a PCB style, but it does have std. wire wrap pins sticking out from the
PCB. If the BDAL17-20's are not present across slots, can I just simply extend them
thru by wirewrapping?
Probably. For the VT103, there were no pins, just the
solder bumps. That was sufficient to attach the required
wires. Note that all of the ABs must be connected, not
just the ABs on the left side of the backplane. For the
VT103 with a 4 slot ABAB backplane, that meant eight
connections per each of the four wires to connect the
BDAL17-20 together (each to themselves of course).
If anyone can shed any light on this backplane, it
would be greatly appreciated.
thanks in advance for any replies.
--
alex
If you have any more questions and you answer the
questions, it may be possible to help some more.
Jerome Fine