Yikes! I checked the PDP-11 and the RK05. I am happy
to report that both
survived the newbie torture test!! RT11 w/ MUBAS is still operational :-)
DEc machines had to be able to stand up to all that Failed Circus could
throw at them :-)
More seriosuly, the signals on both the Unibus and RK05 cables are mostly
open-collector TTL. Interconnecting those at random won't damage any
hardware, there can't even be contention between outputs.
Be warned though that many backplane slots carry power rails, including
those other than 5V. Connecto one of those to a TTL input and the magic
smoke comes out. In partcular, on some connectors, pin B2 is -15V, but
there are M-series flip-chip cards that have a logic input on that pin.
Plugging onbe of those cards into a 'spare' slot jsut to power it up for
testing will let the smoke out (guess how I found _that_ out...)
I never considered the fact that the bus inside the main system is so tailored
to the cards installed within them, especially on a slot by slot basis.
Thatr depends on the machine, the backplanes, etc. In general, the CPU
backplane will have dedicated slots fro CPU boards, They must go in the
right slots. Core memory often has its own custom-wired slots too (for
the core plane, address drivers and sense/inhibit (data) boards), which
may be part of the CPU backplane, or may be another backplane.
For periperhal devices, there are single-board ones known as SPCs (Small
Peripheral Controllers). There may be some SPC slots in the CPU backplane,
there are backplanes of SPC slots too. The inbterrupt and NPR (DMA)
priority is daetermined by whcih slot a device is in (nearer the CPU ->
higher priority), other than that the slots are equivelent.
Other peripheral devices are somplete backplanes full of boards. You have
to put those boards in the right slots in the right backplane.
If I understand things correctly, the first RK05 drive cable is
attached to the bus
opposite the M7255 card. The RK05's are daisy chained together. The last
There are 2 different RK05 controllers used with the PDP11s It sounds
like you have an RK11-D, which is a special 4-slot backplane containing 4
quad cardss (I think M7254 to M7257). This boards must be in the right
slots in that backplane.
You need to get the RK11-D printset, It'll show you where the various
cabels and boards connect. Note that in a lot of cases the backplane
layout is shown looking at the wire-wrap side fo thge backplane, a mirror
image of what yo'd expect. Caught me once...
From what I rememebem the Unibus In and Unibus Out are
in the normal
places, so you can put the RK11-D to the left of the previous
backplane
(or the CPU backplane), put an M920 conenctor betweem Unibus Out of the
previous backplen and Unibus In of the RK11-D, and continue i nthat way
if you want ot add more backpalens. Oh, and put the Unibus Terminator in
the UInibus Out of the last backplane.
One of the remianing 2 AB connectors carries the BC11 cable to the
drive(s). The other carries a power connector and provices a place for a
KM11 test board.
RK05 has an M930 terminator. In the main cabinet, the
M930 terminator
opposite the M7257 card is removed and the BC11 cable leading to the 1st
slot in the TMA-11 is installed. The M930 terminator in the TMA-11 now
becomes the Unibus terminator. If the entire Unibus chain is <50 ft, then we
are good.
Sounds right. Incidentally, don't worry too mauch about Unibus length and
loading limits. They are very much on the 'safe side', and it's very
uncommon for there to be problems.
Are all BC11 cables the same? I see some with M919 connectors and others
with M929?
AFAIK they are all the same. I thoguht the PCBs at the 2 ends were
diffeent, so you could have a pair of tapewires joining them without the
tapewiare crossign over, and without getting a mirror reflection between
the contacts on the 2 ends.
-tony