Roe Peterson wrote:
On 10/25/2013
05:23 AM, Jerome H. Fine wrote:
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.
I've got an original pdp11/03 in a four-slot backplane, _all_ the
slots are Q18/Q18 serpentine. The RLV12 (quad width) lives in slot 3,
the system works great.
I did not make myself very clear. I was stating my understanding
with regard to the RLV11 (two quad width boards) controller
which MUST be installed in two ABCD (or as noted elsewhere
QQ/CD) slots. If the RLV11 boards are installed in two ABAB
slots, there is permanent damage to at least one of the boards
although I don't remember seeing sufficient magic smoke being
released at the time to realize what had occurred.
The BA23 box has 3 ABCD slots at the start followed by
5 ABAB slots. I remember noting an RLV11 board set
installed in slots 2 and 3 with the CPU being in slot 1 as
expected and probably required. The memory was probably
in slot 4.
As for the PDP-11/03 you mention, it is my impression that
BDAL18-21 must be wired - maybe with power on one or
more of those lines whereas with the dual PDP-11/23 CPU
(M8186 board), BDAL18-21 must be either empty (which
is a Q18/Q18 in that case) or wired ONLY to each other
(Q22/Q22). Specifically, a PDP-11/23 (M8186 board)
must not be inserted into a backplane (and power turned
on) wired for the PDP-11/03 (or LSI-11/03). Roe, can
you please comment on this as well and anyone else reading
this thread? I may be mistaken, but this is what I remember.
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?
Assuming the bus is in fact
QQ/QQ serpentine, yes.
I forget who asked that question, but my understanding
differs. With the VT103 backplane which is a 4 slot
ABCD (QQ/QQ) serpentine, if a dual M8196 is in
1 AB, then 2 AB must also be used - either with a
useful dual board or a dual bus grant board. Can
someone else please verify this point as to which is
correct?
While this is all fine for dual cards, but how does
this configuration
handle quad cards?
As long as quad-width cards don't mess about on the
right-hand side
connectors (most of them don't) you can use any quad-width slot,
whether its wired QQ/CD or QQ/QQ.
On this we both agree!!!
One thing to note, however, is that some how, bus grant
continuity is still maintained by a quad board inserted into
a QQ/QQ (either Q18/Q18 or Q22/Q22) slot even though
the quad card accesses the BDAL18-21 lines of only one
of the QQ/QQ pair. This must be true since if a dual card
is placed in one of the QQ, the other must have a second
dual card or a bus grant. So there must be at least a little
bit of messing by a quad board with the "right-hand side
connectors" or the bus continuity would be lost. NOTE
that bus continuity IS lost with the first version of the
RQDX1 quad board. ONLY one of these RQDX1
boards can be used since bus continuity is lost after
that board. But the RQDX1 is the one exception I know
of which does not pass on the bus grant. Note that the
RQDX2 (which I think is call the M8639-YB) which
supports an RD53 does pass on the bus grant and the
M8639-YA (which I think is still an RQDX1, but does
also support the RD52 as far as I remember) may also
pass on the bus grant, but I can't remember right at the
moment. By the way, I suggest that the M8139 not
be used in a VT103 since I seem to remember it draws
6 amps on the 5 volts, probably more than a VT103 can
handle with all the other boards it would need since the
total available is ONLY 16 amps on the 5 volts.
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).
Just a clarification, the high-order four address lines are BDAL18-21...
Thank you for pointing that out!!! I copied the line numbers
from another post (or maybe an early version of this
thread)
and forgot to verify the numbers.
Jerome Fine
